I spoke to GTXVette a couple times today & he gave me some good tips. First I checked the original balancer and was surprised to find the timing mark was actually about 7-degrees before the crank keyway. I tried to check the new balancer, but I couldn't see anything with the crank bolt in, nor could I loosen it without the engine turning, so I didn't pursue it any further tonight.
I did check timing throughout the RPM range with the vacuum advance capped, and found:
-8/9 degrees at idle ~720rpm
-10 degrees at 1000rpm
-23 degrees at 1500rpm
-25 degrees at 2000rpm
-29 degrees at 2500rpm
The only problems are I don't think the timing mark on this balancer is actually correct, and I'm not sure I'm reading/calculating RPM correctly on this multimeter. Because if I were, and the 54 degree total I read last night was correct/possible, I'd probably have major spark knock.
So I simplified...
Knowing that I'd not yet had any knock, I advanced the distributor a couple degrees, went for a short acceleration run, then tried again. I did that 5 or 6 times until I got a slight bit of ping, then backed it off a couple degrees. I pulled out the timing light & and checked my base idle + vacuum advance... 42-degrees. Ok, obviously thats not accurate, ergo my timing mark must be incorrect.
I will say it had much better acceleration, and slightly less hesitation. GTXVette and I also discussed swapping in a heavy advance spring, so I'll try that next time.
One other thing that points towards the timing mark being wrong: all the instructions I've read mention the vacuum advance can should be pointed generally toward the front of the car, but initially mine was pointing over the valve cover. This made it difficult to adjust the lock bolt, as I only had a bit of room between the canister and the carb to insert & try to turn the wrench. With the distributor advanced further I can fit the wrench between the canister & firewall, where there's much more room.
So overall I think it might have been a tiny bit of progress.