Your experience was mixed I think. Partly their fault, partly your unrealistic expectations.
There isn't any excuse for smelly water. I think that is usually because the anode in the water heater has eroded away. It is fairly common to hear about smelly hot water, and as I recall that was a common reason. I've not experienced it personally. Regardless, it doesn't happen overnight, and they should have kept that squared away. You should be able to drink the water, but I definitely would NOT drink the water from any unit that wasn't owned and maintained by me, and certainly not from a rental tank.
On the battery, there could be blame to go around. You might not have experience conserving DC power in a trailer, and you can burn through a single battery fast. You don't mention if you ran a heater, which is the biggest consumer of power, but so is leaving all the lights on for hours on end. I would never try to boondock multiple days on one battery, without having a generator running a lot, and I consider myself very good at conserving DC juice. On the other hand, every previous renter has no doubt abused that battery, running it down far too low, which you did too BTW. But, in your defense, you told them you were boondocking, and they apparently did nothing to load test that battery, or to load you up with a second one, or even to explain some of the basic conservation things you should do. So they definitely share the blame. I'll bet they burn through batteries left and right, get tired of buying good ones, and just put **** on their rentals knowing the customer will ruin them anyway.
Lots of families would chalk this up to a learning experience, all part of the adventure, and not expect a refund.