I used some of this 90KV-rated cambric tape when transplanting a glass CRT into my CTC-4. I still have much of the 20-yard roll left. Send me a PM and I'll mail you some to insulate that spot where the arcing occurred.
I would reserve judgment on the flyback until you can remove the wax and carefully inspect the winding.
Apart from this little incident, if you're getting a good picture from RF input, that sounds like great progress.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html