Are you still getting 0 PSI on the low side and 150 on the high? As long as you have enough freon in the system, this shows that the compressor is pumping and the expansion valve is stuck shut. Even with a low charge you will get spurts of cold air.

From your description you get initial cooling that goes away after a while. If the compressor was bad, the pressures would fall off as the cooling level drops.

A 45 min rebuild is not likely outside of a production environment where dozens are being built at the same time.