drain the hot water heater too.
Im no reference for cold temp storage but we also have enclosed storage but this might give you some ideas....last year i didn't even blow out my water lines (or run any antifreeze thru them).
I have 50A electric service in our bay (but rarely use more than a 15a service/outlet).
i use some hi/lo recording
Thermometer that recorded the low temp (inside & outside) the coach (it rarely gets down to freezing here in texas)....but if it gets close to freezing i turn on some
oil filled radiant heaters.
my storage bay is close to home so when it gets cold i stop by the coach to monitor the recorded temps and turn the heaters on (low)