First the performance difference between 2x and 4x is about zero, so enabling it doesn't help much.
Second various "old" p3/athlon motherboards based on for example Via chipsets don't like 4x AGP much and can be very unstable when using it. It seems your mobo is one of the victims and there is nothing you can do about it.
Wine is a quite special piece of software. You can't compare the results you get on Wine with windows performance since useally it is a lot slower because of various reasons. If you get a framerate of 30fps or higher you should already be happy.... (one thing that could improve performance is the right sound driver for your board that supports mmap sound (dma sound) but I'm not going to explain all that .. you need to enable some option for it in wine ..)