(which all things considered should give you a much higher power level than what you actually have considering Goku couldn't withstand 100g at first, but whatever)
I approach the gravity question from a slightly different angle. Namely, strenght of Ki (and hence power level) and physical durability and strenght don't scale in direct proportion.

Consider the following: Callin weighs around 60 kilos. In 200 G, that becomes 12 000 kg. Impressive for a biological organism to move around... but not particularly impressive to feats like blowing up the Moon, or even erasing a whole city with a flick of your wrist.

The point is, via Ki, most DB characters can dish out far more damage than they could physically, and they can also block attacks (notably, other Ki attacks) that should eradicate them and everything around. I see the difficulties high gravity causes to otherwise powerful characters as being similar to Goku's lethal heart disease - a mundane and surprisingly weak obstacle which remains threatening because it can't be circumvented by Ki.