Any luck with the monitor yet? Judging by the pictures you have the screen volt too high and the colours too low. Also, the brightness and contrast pots are separate from the chassis and might be located elsewhere in the cabinet. The focus sits on the neckboard. Don't kill yourself while adjusting that btw! One hand around your nuts mate - always.
You say somewhere that the colours are wrong. Are they inverted? If so, plug CY/CX is the rgb negative - just move to the other header position (it is a three wire plug of red/green/blue). Also, as you say, it needs to be degaussed.
If, after recapping and adjusting everything there is it's still milky white, there is a chance that the tube is borked.
And in case you haven't found it yourself yet: http://mameandcoinop.xoom.it//mameandcoinop/utility/mtc900.pdf