I'll answer what I can...
The turbo, like I said 12psi is the suggested max, and it probably won't make any more power past 12psi anyway, just increase the risk of it failing....it could last 2 years on 12psi, it could last 2 minutes. Not sure on compressor size sorry.
Suggested replacement, thats kind of a broad question...there's a big selection of size/brand etc so it'll be up to what kind of power/response you're chasing.
I personally run a HKS GT-RS on my 33. Forged bottom end etc, standard manifold, the GT-RS is a direct bolt on. It'll max out at about 270-280rwkw with supporting mods, and is 1 of the more responsive turbo upgrades for the RB25DET.