I am not sure I would want to live in an RV in Oklahoma. So for that reason, I would not consider fixing it and living in it there.
The trailer might not be worth fixing. Or at least putting a lot of money into. If the roof is reasonably clean and Eternabond can be applied properly, then that is a good repair and should not be real expensive. If Eternabond cannot be applied properly, as in around vents, or seams, or where end caps meet the roofing material, then non leveling caulk can work for you too. And not that expensive. If the roof is in bad condition, it could be replaced. But figure $6,000 for that repair. And before doing that, ask yourself what other water damage has occurred over time by the leaking roof. Any black mold inside the walls? Other rotted walls, insulation, and floors?
The tank can be replaced...but again...expensive. Get some JB Weld and try that. You got nothing to lose.
Bottom line, is don't spend much money on this trailer. It is only a temporary solution for you. Do not plan on keeping it. If you decide to use it temporarily, get it out of harms way. They don't hold up well in heavy winds. And offer no protection in a tornado.
BTW, Glad to hear you and your girls are OK.
