What's the story with DW's son? He had the same access to motor home, computer, etc. as DW. (And his younger age makes him a more likely candidate for "pedophile who hasn't been found out yet.") How carefully was he investigated before he was ruled out as a suspect by LE? DW's behaviour (and route of travel) became erratic after he picked up and started loading his RV. Is it possible that he discovered evidence or a body left by his son (or someone else) in the RV and panicked?
I'm not saying I think DW is innocent--I just don't think he's guilty yet.
A good theory, and one that no one else has stated before. It deserves real consideration.