There are others who are likely better equipped to answer some of your questions. At the outset, I would make these points...
1) Be thoughtful on your use of a cover. You say you use the camper often. There is debate over whether covers should be used at all, but I would sincerely question the value of a cover for anything other than seasonal storage. I would caution that frequent placement and removal of a cover could do more damage to your exterior coatings and decor than just leaving it uncovered.
2) During the season, I only drain my fresh water tank once or twice. But, we don't drink from it, and often don't cook with it. I do sanitize each spring - Google that process and it is readily explained.
3) Our FW tank has a little faucet-like drain that is nothing more than a small level that opens the valve.
4) A lot of people use battery-tenders of different sorts for batteries. We have a TT, so I will leave that advice to those with MH's. That said, no need for 30amp at the house unless you want to run the air.
5) We use AC when we need it and run fans when we don't. Not sure we would want the hassle or expense of an additional system.
Good luck!!