Nice set there
. What is the number of the replacement CRT in there? Just Curious.
That thermistor is not required but helps your set's components last longer by limiting inrush current to the transformer.
A type CL-60 thermistor will carry 5 amps and can be used in place.
BTW my first repair, to my childhood TV a 1962 Motorola 19" BW, went exactly like this;
mystery part open= thermistor, hissing crackles=arcing high voltage
Good Luck, Id have driven hours for a set like that too