You seem to have a good grasp of things. Well done !
Doubling the hoz osc freq will cause the hoz out tube to conduct
twice as much & maybe pull down the B+. +- 5% ok but
-10% should give other symptoms like bad width.
Order I go in is power supply then H osc/ HV. At that point you get
a good idea of the condition of the CRT, yoke & FBT.
So for now get the osc on freq.
BTW one of the most common problems after recap is hoz freq off.
The set drifts over the yrs & changing cap puts the "right" values
back in. Also for HV 1KV per inch is a good general rule.
enuf fer now
73 Zeno
LFOD !