Right, if there's something like a small hole in a pressure tank, it's very unlikely to be aligned exactly with the CG, so the tank will spin around and the net thrust will be near zero.

If a pressure tank splits in half, both halves will fly away but that's a very inefficient way of using the energy in the gas, so the added velocity will be a small fraction of the speed of sound in the gas, which is 1/6 of orbital speed for hydrogen, less for any other gas.

You can't really get much of a chemical explosion because the fuel and oxidizer both disperse very quickly in space.