2002 Isuzu Rodeo Question Compressor Noise and Warm Air @ En

For some time now my AC system has functioned poorly. I have not had the time to address the problem until recently. At high engine speed, there is a temperature drop of about 38 degrees. At low engine speed there is a drop of about 8 - 10 degrees which is accompanied by a lot of compressor noise; a very loud steady buzzing. At idle, the low side pressure is about 90 PSI. Far too high. Pressure drops to 45 PSI at 2000 RPM. Only slightly above normal. The high side pressure is also fairly low. I'm trying to eliminate several possible causes: the TXV, reed valves and the compressor head gasket. This Rodeo is fitted with a Zexel DKV14G compressor and a replacement is very expensive ~ $500. I'm hoping the problem is in the TXV. If the reed valves or compressor head gasket were faulty there would be abnormal pressures regardless of engine speed, right? I've stopped running the car's AC out fear that the compressor is sucking up liquid refrigerant, causing the loud noise.

I need professional help diagnosing the problem properly.

Thanks

UPDATE: I Just got back from work and I hooked up the manifold gauge to the low pressure side only. While idling, I watched the gauge as I cycled the AC compressor. At engagement, the low side pressure is about 60 PSI and climbs to 90+ in about one minute. When I rev the engine to 2000 RPMs the pressure drops to 35 PSI in about 10 seconds and delicious ice cold air pours out of the vents. I've noticed that the noise stops exactly as the pressure crosses the 50 PSI mark. Is there an internal relief valve inside of the DKV14G? Also, the condenser fan functions normally. I'm beginning to point my finger at the TXV. Is it possibly stuck wide open? Any replies would be greatly appreciated.