гипотеза о том, что Кадм - в значительной степени отражение библейского Давида:

http://westerncivilisationamaic.blogspot.com/2012/06/david-as-cadmus-part-one.html David as Cadmus (Part One), John R. Salverda
http://westerncivilisationamaic.blogspot.com/2012/02/europe-is-named-after-descendant-of-ios.html Lost Cultural Foundations of Western Civilisation: Europa Lost

при этом получается, что поединок Кадма (Кадм = Адам?, без огласовок КДМ и ДМ) с драконом "накладывается" на поединок Давида с Голиафом? При этом Кадм пригвождает дракона-змея копьем к дубу, что может вызвать все те же ассоциации с христианским распятием, а также с медным змеем Моисея. И опять, очевидно, пушки?

http://www.sno.pro1.ru/lib/kun/67.htm Н.А.Кун. Мифы и легенды Древней Греции. Кадм

некоторые цитаты из статей:

The role of Cadmus in the story about the return of Europa, foreshadows a type of Christian Messiah, accordingly he is made to perform a series of tasks, which are obviously designed to fulfill many key Messianic prophecies

"And I, if I be lifted up from the earth, will draw all men unto me. This he said, signifying what death he should die. The people answered him, We have heard out of the law that Christ abideth for ever: and how sayest thou, The Son of man must be lifted up? who is this Son of man?" (John 12:32-34). Cadmus destroys the serpent by transfixing it to a tree, thus, "lifting it up." "And as Moses ‘lifted up’ the serpent in the wilderness, even so must the Son of man be lifted up:" (John 3:14) "Why, Cadmus, why stare at the Snake you’ve slain? You too shall be a Snake and stared at." (Ovid, Metamorphoses 3.28). ("And the LORD said unto Moses, Make thee a fiery serpent, and set it upon a pole: and it shall come to pass, that every one that is bitten, when he ‘looketh upon’ it, shall live. And Moses made a serpent of brass, and put it upon a pole, and it came to pass, that if a serpent had bitten any man, when he ‘beheld’ the serpent of brass, he lived." Numbers 21:8,9 "they pierced my hands and my feet. I may tell all my bones: they look and ‘stare’ upon me. They part my garments among them, and cast lots upon my vesture." Psalm 22:16-18),

в англ. библии змей Моисея "огненный" (fiery) и поднят на шесте (pole), в русском синодальном же переводе змей поднят на знамя (Константина Великого?). Предсказание Кадму определенно перекликается с 21 (22) псалмом Давида, где речь как будто о крестных страданиях Христа.

The transfixed serpent, with it’s triple tongue, and it’s triple row of teeth, would appear, to a Christian, as the law (with it’s triple format, commandments, judgments, and ordinances) fulfilled ("Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill." Mt. 5:17).

In this act, the myths have Cadmus winning a nation, a kingdom, and a bride. In reading about his wedding banquet to his new bride Harmonia, which all the gods attended, one cannot help but be reminded, of the long awaited, "marriage feast of the Lamb." (Revelation 19:7-10)...

Take note that the Christian Messiah at his death fulfills prophecy by becoming like the snake in the wilderness and that this prophecy was apparently known to the ancient Greeks who told the "myth" of Cadmus.

The Phoenicians who founded the Greek Thebes brought the story of David to Greece, (Could the Alphabet have come without a few current stories written in it?) he was something of a culture hero to them, they knew him as "Cadmus." And in the story of how Cadmus founded Thebes, they apparently used the story of how David founded Jerusalem, for in as much as David was the founder and first king of Jerusalem, so too Cadmus was the founder and first King of Thebes.

Now, as to why the place was called "Thebes" instead of "Jerusalem" I suspect that this is where the identification of King David with the Egyptian Pharaoh Tuthmose I (postulated by Damien Mackey, Dr. Ed Metzler, and a few others) comes into play. Before we get into the triple identification, let us look into some points of coincidence between the Greek myth of Cadmus and the first part of the historic David's story.

Давид = Тутмос I? Во всяком случае "...Тутмос лично поразил нубийского вождя копьём, и, несмотря на поддержку кочевников, вторгшихся из пустыни, враг был полностью разгромлен. Затем Тутмос I продолжил поход вверх по Нилу, а труп побежденного нубийского вождя был повешен на носу лодки вниз головой для устрашения всех непокорных племен Нубии." http://ru.wikipedia.org/wiki/Тутмос_I
Может быть, это отражение поединка Давида и Голиафа?

Casting the Stone
"Cadmus ... with a straight cast of the stone smashed the top of the dragon’s head; then drawing a whetted knife from his thigh he cut through the monster’s neck. The hood severed from the body lay apart," (Nonnus, Dionysiaca Book 4. 406) David also cast a famous stone that smashed the top of, not a serpent's, but a giant's, head. He also followed up by cutting the head off. "David ... took thence a stone, and slang it, and smote the Philistine in his forehead, ... Therefore David ran, and stood upon the Philistine, and took his sword, and drew it out of the sheath thereof, and slew him, and cut off his head therewith." (1st Samuel 17:49,51) How many times, in either history or myth, can you find such a story? An ordinary man engages in single handed combat with a gigantic monster, he tosses a stone, hits it on the head, and knocks it out. Then he runs up on it and cuts it's head off with a sword. These specific circumstances comprise a fairly rare story, and yet David and Cadmus hold it in common. The question arises; Why would the Greek myths recast Goliath, a giant, as a serpent? As a giant, Goliath was called a son of "Repha," one of the Rephaim. To many who have studied comparative religions, these Rephaim were analogous to the Earth-born Giants of Greek mythology. However, the Greeks considered the Earth-born Giants to be serpentine in nature, either having serpent legs or serpent hair or both, (see the frieze upon the altar at Pergamon);

...It therefore seems plausible at least, for the Greeks to have pictured Goliath, a Giant, as a serpent. (Schickard, Novidius, and other biblical scholars said that the constellation of Perseus, with the head of the serpent haired Medusa, was David with the head of Goliath.

...enigmatic Scriptural statement; "And David took the head of the Philistine, and brought it to Jerusalem;" (1st Samuel 17:54). Some take this statement to be an apparent anachronism, for Jerusalem was still in the hands of the Jebusites at the time. A more likely supposition, however, is that Golgotha (skull place), just outside the walls of Jerusalem, was the site of the burial of the skull of Goliath. Thus Christ, in his death, figuratively bruised the head of the serpent just where David placed the bruised head of the giant Philistine. "And I will put enmity between thee (the Serpent) and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shall bruise his heel." (Genesis 3:15). David perhaps displayed the head of Goliath upon a wooden stake as an ensign warning the Jebusites of his eventual victory against them as well (thus giving a justification to Ovid for his version of Cadmus' killing of the Serpent, whereby it was transfixed to a tree nearby the site where Cadmus was destined to build Thebes.).
Cadmus, like David, wore no armor protection for this, his defining battle. "Cadmus, ... Clothed in a skin torn from a lion," (Ovid, Metamorphoses 3, 50) David famously claimed to have killed a lion (earlier in that same day, according to the Quranic version of the story). In my view, the fact that Cadmus performed what seems to be an obvious messianic task, (wounding the head of the serpent) dressed as a lion, is steeped in meaningful symbolism. The lion is the totem of the tribe of Judah and especially of it's King David. ". . . behold, the Lion of the tribe of Judah, the Root of David, has prevailed . . ." (Revelations 5:5).

Regardless of the minor chronological and geographical discrepancies practically every feature of the "myth" of Cadmus founding Thebes can be shown to have had a Scriptural origin in the story of King David.

змей Кадма обитал в гроте, не напоминает ли он этим бога Пана (аллегорию пушек), который также любил отдыхать в гротах?

близость понятий "Кадмова победа" и "жертвенный агнец":
http://en.wikipedia.org/wiki/Cadmean_victory (Greek: Kadmeia nike) is a reference to a victory involving one's own ruin,<1> from Cadmus (Greek: Kadmos), the legendary founder of Thebes in Boeotia and the mythic bringer of the alphabet to Greece.<2> On seeking to establish the city, Cadmus required water from a spring guarded by a monster snake. He sent his companions to slay the snake, but they all perished. Although Cadmus eventually proved victorious, the victory was at the cost of lives of those who were to benefit from the new settlement.<3>
See alsoPyrrhic victory
Sacrificial lamb

http://en.wikipedia.org/wiki/Sacrificial_lamb =жертвенный агнец
An example of this in early literature is Macaria in Heracleidae by Euripides.
See also
Cadmean victory, in which a sacrificial lamb either loses a battle or dies but whose actions lead to a greater victory
Cannon fodder, an expression used to denote the treatment of armed forces as a worthless commodity to be expended
Forlorn hope, the initial wave of troops attacking a fortress or other strongpoint, who usually took horrendous casualties.
Lamb of God, a direct reference to Jesus Christ who, in death, is traditionally considered to have played the role of a sacrificial lamb
Korban Pesach, also known as the "Paschal Lamb"

Paschal похоже на "пешка" - тоже фигура, приносимая в жертву (другое значение - марионетка)