I am curious too. You are at the point where I was when I gave up. Could not get the system to draw down to a good vacuum. Since I was using R-12, getting a seal was important to me.
Craig

2014 Ram 1500 Laramie, 73 Cuda
Previous mopars: 62 Valiant, 65 Fury III, 68 Fury III, 72 Satellite, 74 Satellite, 89 Acclaim, 98 Caravan, 2003 Durango
Only previous Non-Mopar: Schwinn Tornado