Idle Rpm High in Park, Low in Drive

Dart,
Congrats! You are going in the right direction.
Couple of comments/thoughts:
- stop messing around with total timing & dist curves, get your idle timing sorted FIRST.
- I have never seen a 650 rpm drop going from N/P into gear in your situation. I guess it is possible that it is just 'your' combo, but to me it seems something else is amiss. A large stock c'ter loads the engine more than a stall c'ter, so if this is what you have you get a bigger rpm drop going into gear. Still seems excessive though.
- you got 25* in Park? Did you check in gear, at idle? If not, this is likely your problem. Less than 25* means either the centri weights in the dist were activating &/or the VA unit was unable to hold with the reduced vac in gear. It is imperative that you use an adj VA unit & set the Allen Key fully CW as a starting point.
- the choppy idle, high @ 1100 rpm low vacuum I assume is from a sizable cam in the engine. 25* in gear is not a lot, & your combo is probably going to need a LOT more for best idle. Like as much as 40*. GM used MVA. Pontiac V8s with 10.75:1 CR, small cams that idled smoothly at 600 rpm left showroom floors with 26* idle timing.
- while I do not think it is the cause of your problem, you should check/verify/the transfer slot in te carbs primaries. 0.040" or less is what you want.
- mixture screws. Adjust for best idle quality [ sound/feel ], not highest vac, although vac will be high.