1. Do the 3 walls around the tub and the rest with regular rock. Add a large exhaust fan.
2. Yes there are other products for tub surrounds that come in sheets other than the man made marble, Check with a large building supply in your area, the product is like masonite with a laminate face. As far as tile you can attend seminars at the big box stores, if you are unsure of doing it your self, buy some materials and practice. For $1100 I think I would learn to do tile.
3. Tile counter tops look nice for a while but in a bath they become filthy fast, I would opt for P-lam