There's a good chance the problem is related to all that corrosion. The adjustment pots look like they could be damaged, or dirty. The sub contrast control could cause no video if it was open circuit.
Since you have high voltage, I would try turning up the screen/g2 control (usually on the flyback below the focus control). No matter what the video circuit is doing, you should be able to get something on the screen. It might just be a blank raster with retrace lines, or there might be something on the screen to give you a clue.
What voltages do you measure on the cathodes? Those are labeled R, G, and B. Also G1, and G2 would be good to know. Do the R, G B, or G1 change at all when you adjust the brightness, or contrast controls?