Only a little help, I own a DW-8000, and have the manual, but offhand, I know (or believe) that MIDI controllers can be manipulated live (volume, pitch, pgm changes, etc.) can be done via MIDI, but I don't believe you can call up parameters and change them from a MIDI source. To do so would require you to change from Patch to Parameter mode remotely, I don't recall that you can do that. I'll take a look at the book and get back to you, but it was a very early MIDI capable keyboard, and since it could only recall one parameter at a time, I doubt there was that kind of flexibility.
On a side note, these older keyboards are fun to play with, and do their thing very well, but I would be cautious trying to lug them around for live performances. Back in the day, I had a friend who worked almost exclusively with a DX7, she said it could often surprise you by forgetting all its patches, losing output, etc., and that was when it was new. I recently got interested in performing live (after a 20 year (kids) hiatus). While my DW-8000 still works, it has been at least that long since I changed the battery in it. I did copy its memory to a digital recorder, but that still needs done. My EPS (Not the greatest sampler, but a great controller keyboard) went poof shortly after I started with it. My point is, while they are fun to fool with, I would be concerned about their longevity. It might be worth it to look at a Motif Rack, or some other items, that provide a number of the sounds from those earlier keyboards, with the reliability and flexibility of much newer pieces. Just my $.02, as a "serious" hobbyist.