As to your Horz AFC diodes, I wonder if RCA's patents would be infringed, yet the GE is mainly an RCA clone. The 6BH11 and another few tubes were GE's finishing touch. The only CA I saw was in HS, where we had one with a dead red gun so

nobody wanted it, as we thought a bad CRT meant death to any TV 40 years ago. Who knew they were so interchangeable and you would still find good CRT's in otherwise abandoned TVs.
The sync is indeed messy on this 16x and that garbage riding signal can be traced all the way back to 1st video stage. I am spending too much time going in circles, literally circling back to the same places to find where the phantom junk originates.
When I get back on the 16x, electrolytic caps will all be replaced, like SOP on any vintage set. But Im not sure that is the cause because bridging all the PS caps with an 80 uf / 450 v did not produce any improvement. Then again, this still could be THE whole problem.