Well, you need to realize that Mettius was developed, spelled and pronounced in Sabine, not Latin which is a completely different language - it has even been argued that the Sabelinne languages were parted from Latin already after the PIE (proto indoeuropean) stage. Very early that is. It is therefore impossible to connect to Latin in the way you do.
Further on, there is no relationship, as far as I know between, between the names Mettius and Matthias- - the latter comes from Mattitjahu (hebreic) and was transferred to latin by the Greek transcription ???????. It's thus simply a coincidence that they look similar to us today.
On the matter of DIVI: DIVO IVLI is simply a an abbreviation form (to fit easily in inscriptions and coins)of divo julio which is Divus Julius, Caesars post mortem title, in the dative or ablative case. Nothing strange at all.
I guess that Theos could be used for divus, but ???????? (Sebastos) was, in my experience, much more common as the emperors title in the Greek world.