Egads, that's pretty dirty. The extended functionality will be dropped by your converter, so if you can, you'll want to use PS/2 directly, or modify hasu's or soarer's adapters to handle those extra keys -- hasu's, at least, is pretty easy to add that to, not sure about soarer's, as I haven't used it. I would assume it would be just as easy in either of them, honestly.
You are definitely going to need to clean that bad boy. Not sure if you have any interest in a bolt mod, but it would make it much easier to clean it up, since it would be fully disassembled, plus you can change the layout to ANSI instead of that almost ISO.
I haven't looked at mine, but I wonder if there is a jumper on these similar to what the Unicomps have, so you could swap between unique (but converter dropped) scan codes on the extra keys and modifier based extra keys, which would pass the converter, but couldn't be used directly by AHK, as far as I know.
Regardless, welcome to the 122 club!