Welcome to the forum.
I watched your video and a couple of things I noticed. You pointed to the low point drain decal and said it was actually the fresh water drain and it was on the other side of the trailer. Usually low point drains are two pipes exiting the trailer which allow you to drain the fresh water system and has nothing to do with the water tank. Look again real close below the decal on the same side. It may be just 2 open ended pipes or they may have a valve or just a cap on the ends of the pipes. The valves could be inside a cabinet. If you can't locate the actual pipes anywhere beneath the RV, ask the dealer where they are.
The other thing you mentioned is replacing the triangle in the rear because it got crushed. If it looks like it's going to be a reoccurring problem, I would highly recommend something on these lines except either welded or bolted to the frame. http://www.etrailer.com/Skid-Wheels/Ultra-Fab-Products/UF48-979014.html?feed=npn&gclid=CMjAw52Bgs0CFYFahgodGcMGfg