From what I have read, it soulds like you got one hell of a hack on your hands.
Refrigerant pressures mean nothing to me. Refrigerant levels mean everything. and theres a lot that goes into this calculation....just as mentioned before: indoor DB/WB/RH, outdoor DB/WB/RH, suction pressure, discharge pressure, liquid pressure, liquid line temp, suction line temp, suberheat/subcooling calculator. We take all these readings and sometimes more to properly diagnose a system.
Your tech couldn't get the pressure to rise so that automatically qualifies as a bad compressor???? Its scary that he made it through school with them smarts.
You need to find a reputable contractor. One that is more than willing to send a tech out with no time limit. I don't work on time limits. I work 1 call at a time. If it takes 6 hours, then it takes 6 hours. Never again will I even attempt to come close to halfassing a diagnostic.
Get another company out. And see what they say. There has got to be something simple going on. Obviously, your current contractor can't figure it out. And the more the system runs improperly, the more damage that could be done. And the more damage leads to more future failures. Yes, even a clogged drainline is bad when not properly taken care of.
Any more questions??? just ask. We are here to help best the man will let us.