[Electronic M]

I've seen worse flybacks work and live for years.

Most color sets use the B+ boost (which is made from energy recovered from the flyback) to power atleast part of the vertical so if the boost is dead or weak that can kill the vertical.

Make sure the H output cathode current is atleast 10mA lower than the Sam's maximum and of course set it to minimum.... adjusting drive and linearity is good but you may also want to grab a variac and vary line voltage up and down from a starting point 117V to see what line voltage gives Lowest H out cathode current while maintaining full horizontal deflection. Switching from tube to SS HV and focus rectifiers reduces load on the flyback and cathode current and heat since those tubes normally draw their heater voltage from flyback windings.
On my CTC5 special I have added a HV adjust potentiometer. The CTC-7* has a HV pot and is almost the same circuit as the CTC5 special...all I had to do is remove 1 resistor and replace it with another resistor in series with a pot (which I had to drill a hole to mount)...my set with the reg pulled and a medium brightness picture can produce 22KV (other sets that used the same CRT were designed to supply 25KV) and IIRC the CTC5 super schematic falls for 19-21KV before installing the pot it ran at 18KV and afterwards I set it to run at 21.5KV. The HV regulator works by sensing HV level (IIRC boost varies proportionally and is the control reference) and increasing the load on the flyback to reduce HV level....so the less the regulator lugs down the HV the less load there is on the flyback and the cooler it runs... just don't exceed the maximum schematic recommend HV level by more than 2KV as that could strain the HV insulation on the flyback and cause harm.

*Both the CTC-7 and CTC5 super schematics are posted on earlytelevision.org under color sets under technical documentation under RCA....I used those documents to figure out how to copy over the CTC-7 HV adjust pot circuit to the CTC5...It is easy.