Hey mate im new on here but have a suggestion for your backglass.
I have always used playfield ( 3m brand ) mylar for any flaky glasses and have neveraad a drama other than the occaisional air bubble if its not applied correctly.
I can see why you want to stick the paint to the glass initially and that sounds like a good idea but i would seal it with mylar if it were mine.
I always would worry that the TT may crack at some stage and crack the paint as well.
this cant happen with mylar.