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the problem looks to be a bias issue for the CRT assuming the CRT test ok.
the G1 to cathode voltages have a lot to do with the cut off of the electron flow from the electron gun, the G2s look ok, not sure about why one was a lot lower, I presume that was the green.
The CRT cathodes are high, indicating a weak video out tube or a bias issue (brightness circuit applies a bias voltage, the more neg the control grid of the video out, the less current flow and the less of a drop on the plate load resistor, the less drop (higher plate voltage) the higher the directly coupled cathodes of the CRT. Since the voltages there seem high in relation to the G1 voltages you need to determine the cause (video out tube/bias too low/screen voltage too low/emissions too low all reducing the current flow of the tube resulting in plate voltage too high).
if the tube is ok, and the bias voltage on the control grid is ok, then about the only thing left is the screen grid of the video out. this is supplied by the 140v supply which comes from a stacked b+ derived by the voltage drop across the audio out tube.
The other possibility is the CRT G1 is too low. this comes from the plates of the 6Gu7 difference amps. again you need to look into bad tubes but this time it would not be weak but rather gassy or grid emission problems upsetting the tubes and causing too much conduction dropping the plate voltage (the opposite prob of the video out tube), and direct coupling to the G1 of the CRT too low a voltage (160ish)
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