[old_tv_nut]

Horizontal output/sweep is a switching circuit, not a linear amplifier, and the current is not set by the tube, but by the B+ supply voltage and the yoke/flyback inductance (which is how you get a sawtooth sweep current: constant voltage across an inductor). If the current was regulated by HO tube conduction, the tube would be vastly overheated and burn out. If you must have the AGC and burst gating pulses from the flyback, I think your best bet is to leave the circuit as it is and let the regulator do its job.