How to find AC Leak? ... need advice... please!

Oh no! Not another AC thread! I know! But I need help.
So here it goes... AC didn't work since I got my 85 300D. PO's mechanic said compressor leaked. That was about 2 years ago. I decided to try and fix the it. The system didn't have any pressure and before I started, I applied 20 psi of air to the low port and it leaked in no time. I was able to hear the leak at the compressor. So here what I did:
1. Removed compressor, expansion valve, and dryer.
2. Flushed all lines, evaporator, condenser, and pushed compressed air to push it out. Messy job!
3. Replaced o-rings at: expansion valve, dryer, hose junction next to the low port.
4. Installed new expansion valve.
5. Drained and added 2 ounces of PAG oil to new compressor ( that's all it can hold without dumping it all while installing ), and installed it. What a pain! I was able to only torque the hose manifold to the compressor using only about 20 ft-lb. My big torque wrench won't fit. The instructions with the compressor said 25 ft-lb. Used green seal washer on discharge side and NAPA TEM 407279 on suction, no pilots.
6. Added 4 ounces to new dryer and installed it.
7. Added 2 ounces in the suction hose near the low port.
8. Closed the system.
9. Applied vacuum for about an hour. It reached 29 after a few minutes. But it won't hold the vacuum. When I stop the pump, the vacuum will drop slowly, but you can see the gauge move looking at it for a minute. I disconnected the hoses and let it sit overnight just to rule out the manifold tool. In the morning it had 0 vacuum.

So what now? Any idea's? Any way to find the leak without needing to eventually remove the compressor in order to drain it and add the correct amount of oil?
I can't think of any way to find the leak while on vacuum. If I add compressed air and try to hear the leak, will I need to flush the system and replace the dryer?

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1985 Mercedes-Benz 300D (Benzoil)
2000 Toyota Celica (Liquid Silver)
2004 Honda VTX 1300 (Cylon Raider)