Need a new air compressor
First three rules of compressor selection for blasting-
1- CFM
2- CFM
3- CFM
(*4) psi and gallon capacity mean almost nothing as you will exhaust the tank almost instantly unless you have 50 CFM
You are right about 12 @90 being about the minimum for any semi-serious blasting.
My 1980's Bel-Air model 318 (was originally a 338 converted to 220 from 3 phase with factory parts) keeps up great with my medium sized cabinet.
As long as you're above that 15-20 @90 I don't think you can go wrong with Quincy, Bel-Air, Speed-Aire, even IR for Mid-level equipment.