Hi,
I am Ps2cho's father and have been working on this with him...
He is working today, so let me answer a few questions to speed a solution.

Yes, the system was vacuumed using an 5cfm industrial electric pump, and held the vacuum no problem. Reading was about 70hg or -25-30psi and we left the pump on for about an hour. We left the Vacuum in, and charged into that.
We were given 20+ NOS SERCON 12oz cans of R12, and thats what we put in using a side tap.
We put it in as a gas, as were were concerned about putting liquid in.
First can got real cold going in, and second can was not getting cold at all.
I am gonna go out in a min and get some static and jumpered pump readings...

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2009 Mercedes ML320 Bluetec