Is it possible to extract a fix for a game out of XP's compatibility database and put it into Windows 2000 via the Application Compatibility Toolkit?

Nope. Simplest way is to write down the details.

Ok, then, however, how does MS create those fixes. When I attempt to copy a fix, I can only add executables, I can't even do the things that MS has done, like being able to accomodate for temp files and stuff. If you look at the XP database for a game like High Stakes, you get all of these extra files, I don't even know you could do that with the tools available.