from what i gather, he is using a prog (the download link for it is in the text ) to assign keys to controls yeah....(there are 128 midi commands) so you might need to configure em for what you want.... e.g midi 7 is volume IIRC)
not sure on the usb keyboard to midi, but i'm sure there must be something out there.....ive used my qwerty to play keyboard midi notes before..a long time ago..
i guess you'd have to download the appropriate qwerty to midi prog and try it...
i don't use ableton myself, or i would try it...
i use cubase/reason...but iv'e been out of the loop (pardon the pun) with midi for a while....
he tried his on pc and mac....and saiad it was fine....