Don't worry about the vac advance now. It's not something to be concerned with at this point.

Was the cam degreed when installed or dot to dot? It may be out if not degreed.

If the distributor is locked out, just time it for your idle setting 20-22* and start adjusting the carb. Check the rotor for movement. I think I mentioned see if it twist CW and that was wrong, it should advance CCW. If it doesn't move at all, then it's locked out.

An old trick to keep initial in range to not drag the starter was to install a very light spring to keep mechanical from kicking in. It was just enough to keep the weights from moving out when starting, but, once fired, and up to idle RPM, they were all the way out, fully advanced. This may be what's going on with yours. Not my favorite approach.

An MSD billet is easier to dial in than the MP stuff especially if it's an old model MP. Only issue with the MSD, is they don't provide a bushing large enough to limit mechanical advance to what you need. The new MP ones are a breeze except for springs.

What's the idle speed in park? I'd expect that engine to be able to idle in park at 1K and about 850-900 in gear.

I'd rather be working 7/12's than 0/24's