I am sorry to hear that things haven't gone well for you. It's strange, maybe the Apollo Pro + GF2 is a dreadful combination... as I said, I am running 4191 with a GF2 MX 400 and things are fine most of the time (I only say that because I've already experienced some nasty lock up once when I tried to run Quake3 -- even though Quake3 does usually run fine here).
Are you running GNOME? There have been many posts on the official Linux driver forum
about people experiencing probls with GNOME (mostly slowdowns), and these probls going away if they try something else. I am running AfterStep here, even though I run many apps which use GTK2.
It did seem you've done all you could, I can't think of anything else I could suggest. Sorry
Guess we'll have to wait for the next drivers to come out...