Freon is in gas form until it is highly pressurized by the compressor, then it's in a liquid state. Then when it goes through the expansion valve it reverts back to a gas and that is when it chills. (Ever use canned air? Can gets cold as you release it) If you released pressure from the low side, it was in gas form at the point in the system. Don't open the high side, especially while system is on. This is an extremely simplified explanation.
I think you may have a bad relay, or fuse. Then again, your compressor clutch may not be engaging for another reason. If you have 100psi on the low side... it should work. Actually, not possitive about this, but 100psi sounds too high for the low side. I think it's suppose to be between 70-80psi.
I'd put a VOM on the clutch energize wire and check to make sure it's actually getting voltage when A/C is turned on. (cut wire?, bad fuse?) Have someone watch the compressor to see if the clutch even tries to engage.