I guess nobody is yes to both questions, so I'll try from just the first. (I've never tried autohotkey.)
Is this the USB model or the AT model? If AT, are you plugging it into a PS2 port with a passive adapter or using a USB converter? Because I wouldn't be surprised if some of the latter lost the extended codes. Do they input nothing at all or duplicate a regular code (like
y for
ON or
i for
BYE)?
I don't know where Windows gets
SC062 as described on the
page linked to in your other post here. But, according to my notes, what it sends is more sensible than that suggests. The custom extended codes start with
E2, just as some of the standard ones added after the original protocol start with
E0. (And Pause starts with
E1.)
Soarer's doesn't help because that prefix gets dropped in the first conversion stage.
My thought was that the best bet would be to extend QMK to build a converter, since it already has the low-level PS2 input routines from TMK. I sketched out how that'd work but then discovered I'm out of the right DIN parts here. I'll update here when I get back to it.
Were you thinking to put some interesting keycaps on all the funny keys?