Timing help for '64 Dart, 225 CI

I'll try to answer as much as I can. 64 dart, stock, 225CI, single barrel carb. I was told to use 91 instead of the "lead" additive to prevent knocking/pinging? If I remember right...

Yes, timing increases with engine RPM then stops advancing at a certain point.

Vacuum gauge is being hooked to a small port right on the intake for #6, part of the intake manifold.

Timing light is being hooked to #1 plug wire and yes, I did verify TDC as accurately as possible, the marks have not slipped.

Problem here is that I've already gotten a few different answers for how to "do it right" :p

@MV8's post makes sense, as I basically did what they said in the last 2 sentences, e.g. finding a sweet spot of higher RPM at idle, and not-so-hard cranking.