Another lady! Sweet! Not many of us around here. Love the dog, guessing she's part herder type breed? Can't help with the technical goods of the bus, sorry. But I love the fact you have curtains
Other than Smitty, I think you are the only one who has curtains of any sort -sorta- put up.
That water tank, if you do decide to go with something different, might check local soda shops and distributors. They tend to have 15, 30, 55 gallon barrels dirt cheap. Would need a good cleaning.