If I were you, I would take photos and document everything. I would then disconnect the tank from all lines and fittings and refasten the underbelly as securely as possible. Tow the trailer home and call Starcraft customer service first thing Monday morning. See if they'll work with you on getting it in somewhere for repair (I would avoid a Starcraft dealer that wants to charge me $2,800 to take care of a warranty problem - that's immoral). Starcraft isn't the only brand to have issues with the straps and support for fresh and waste water tanks, either.
Rob