1.5x the speed of a bog standard A1200 is to be expected of an '030 with no fast ram expansion. If I understand your post correctly you've already tried it with different sticks of ram, and attempting to run the ram config utility (or autoconfig the ram under 3.1) is causing it to crash, correct?
If you've already triple-checked that any jumpers are in the right positions and that everything is clean, I'd suspect the ram socket might be faulty.