Is your choke not closing all the way? That could explain your cold engine issues...
I had the vacuum advance hooked up on all of the Duraspark conversions I did years ago. You want it hooked up and working, otherwise you have no spark advance.
This reminds me of all the carb issues I had with my old '85 F250. That stupid thing was always not running well, leaking, backfiring... didn't help that it sat for months at a time, but it seemed like I would get it dialed in and running good and then I'd have to tinker with it again in a couple months. The worst one was when the Carter carb started giving me fits and I rebuilt a stock Holley for it... So much worse, ran like ass and backfired through the carb on the highway. Rebuilt the Carter and life was good. It was always simple, easy to fix things but it happened so often...do not miss that.