1. yes
2 & 3. Focusing on the rate rather than just discount. U might get a higher discount but with higher rate and higher service fee. So do ur own calc.
Don't know much about the services and u could discuss with them, but might not be able to get the deal.
4. Your convayncer should do this for u. But u might need to contact the water company to update ur address. It can be find on ur sec 32.