Holy crap... I think that everything I need is actually connected... and that it just needs to be put into TMDS mode, which can be done by setting a register!!!!
I.e., the Cable Adapter Detect line is used to set some register in a way that flips it into TMDS mode. So the problem here is getting the signal to the video bios, but this isn't strictly necessary if the either the bios sets it into TMDS mode BY DEFAULT, or if some other mechanism is used to flip it into TMDS mode.
This is usually part of the video bios.
Now I just need to figure out WHAT REGISTER, and HOW TO SET IT.....