Dear Narkissos,
I think you make many fine observations. As to your question, I don't have any reference at hand. But I'm sure that one has found the trigramm IAW ("IAO") especially on magic amulets etc. I think one has related these artefacts to some kind of Gnosticism.
I have found the following book very useful:
Sean M. McDonough: YHWH at Patmos: Rev 1:4 in its Hellenistic and Early Jewish Setting. (WUNT 2/107) Tübingen: Mohr Siebeck, 1999.
McDonough covers most if not all relevant points. He make interesting comments on IAW too.
Of course he rejects Howard's thesis.
(Regarding the Book of Daniel; I think the tetragrammaton is a relic from the original version.)
Regards
- Augustin -