Still trying to map out a timing curve

You seem to be all over the place. At one point you are saying timing is 'locked out' but only refer to centrifugal advance. Then you are describing advance curves where you have timing retarded at the same time advancing very slow. What exactly are you trying to achieve?

I agree with the above assessment about timing being all in by 2,500 or even earlier. As an example, some of the old MP race distributors came with curves that were 'all in' by 1,200 rpm which was essentially like having locked out timing. The reasoning behind a very quick curve like that is that cars with big cams (like yours) tend to idle over 1,000 rpm, produce low vacuum and spend little time under part throttle operation. Why mess with an advance curve if the combo does not require it? People also run these types of curves on the street without issue, (like me) you just need to make sure you don't detonate.

Your initial timing could be higher as well, no need to retard it much if at all unless your starter can not handle it and it kicks back. I have 20 degrees initial on my solid-cammed small block and it starts fine, no starter kickback. I had it at 26 at one point and it still started fine.

If I can infer what you are trying to do, you need to figure out how to arrive at your desired total advance of 36. Generally, the idea is to limit mechanical advance to be able to arrive at the total (36) while running as much initial as your combo will allow. This is likely somewhere between 18-22 depending on how much vacuum you have at idle. Your car may be somewhere else but whatever the initial number is, you should figure out what it 'likes' first. So let's just say you wind up with 20 initial and it starts and idles OK. Add 16 mechanical (centrifugal) to that number to get 36. That's it.

So now that you have your total figured, your 'timing curve' (or advance)should have any and all 'timing' stop advancing or be 'all in' by 2,000 rpm or so. 4,000 rpm or anything above 3,000 rpm for that matter in a combo like yours is way too late to not have the timing fully advanced. Essentially your timing is being retarded until that point which is probably why it runs like crap. Luckily you have a programmable ignition which should make it pretty easy to nail down. Obviously you have to make some adjustments, take it for a ride and see what happens but that should be your procedure.

Without the digital gizmo you'd be welding advance plate slots and sitting there with a timing light and a vacuum gauge trying to dial it in. (like me)

Hope that helps.