You should carefully inspect the wall board for any damage. If the paper "skin" of the wall board has peeled off with the wall paper, you will have to patch that before you can paint. Otherwise, I would recommend a good quality latex primer.
I have tiled to the ceiling in my shower room because this will stop the wall getting damp. I suppose the real answer to your question is tile as high as you wish. Consider how well your bathroom is ventilated.
If correctly installed there shouldn't be much damage done to your wall with this LCD TV mount. At the most there should be a few small holes from the insertion of screws. If installed correctly, this will do no more damage than if you were to hang a picture frame on your wall.
Well, you need to find paint that goes on dry wall, I'm assuming that is what you have since that is the most common walls to have. You can just go to walmart and tell the people what kind of bathroom you have, and they will set you up.
Glue of any kind is not suitable. -You must pull the sink away from the wall and re-screw the 2 brackets that hold it in. They may not be in the studs, or may have corroded. Mechanical means like this is the only way.