I was reading comments elsewhere on spacers, and the complaint wasn't that the spacers themselves might break, but rather that they put a LOT more stress on the lugs, even very small distances like 1/8th inch. They said that they might be fine for a gently driven car where the owner wants the look, but really bad for race performance with lots of turns... precisely the sort of driving you're talking about. Note that I know nothing about the topic myself, just repeating what I read.
If you want more than 12psi, you're going to have to go off the stock tune, which deliberately limits the turbo to that level for reasons nobody has been able to guess thus far. Trifecta moves that limit up to around 22psi, and I've seen people talking about other tunes and setups that go even higher. The increase in available power is immense.