[old_tv_nut]

Looks like you've got it!
The offset you show with a question mark is the pulse that you saw before the sawtooth when you were accidentally not in XY mode. If needing the horizontal position set to max left is annoying, you can try switching to AC coupling on channel 1 (X). You can watch to see if the waveform shape changes. If it does, it's still OK to use it even if the *shape* doesn't look exactly like the Zenith manual. The important thing is the relative amplitude (vertical) at each marker, which will be good as long as channel 2 (Y) is DC coupled.

The Zenith manual should tell you what percent of peak each marker frequency should be.