To your problem with the screen that I know are three that we have mentioned.
To me it has happened to me 4 times in 3 weeks, the phone does not go out, just the screen, nor is it known why or really even know if it will happen, what we have done is simple:
-Settings -> Display -> Sleep -> 30 minutes put him
I'm trying, now I have to 1 minutes is fine at the moment, the problem is if you put 15 or 30 seconds.
Anyway, if you feel like flashing the ROM ponle that have already taken, it comes with root, with several problems solved (less GPS), probably no longer spend more with another ROM.
If it happens, we're screwed, so clear.
Regards :)