Damon is still my lead suspect. He had opportunity and possible motive - rage, incest, or cover-up of accident. That stupid dog had something to do with it. It pee-ed or barfed, or chewed something up. Damon beat the dog to make it bleed. Perhaps Danielle came to dog's rescue and Damon went off on her, smashing in teeth and accidently killing her. Perhaps he threw her down the stairs. He was pumped up on beer and MJ.
Reminiscent of the Jeffery McDonald "Fatal Vision" case. His daugher wet in his bed and it set him off - he killed his whole family.
Damon got rid of the body before pizza gang came home. Then he steam cleaned the MB, where it happened. He was nervous about the stairs, too, because he cleaned those up the second night. The whole act about preserving Danielle's room because "something evil happened there" is just to throw LE off the path. Same with the magnet trick on the alarms and the open doors. Damon had to make it look like Danielle was taken from her room AFTER Brenda came home. That's the time when Damon has an alibi. After DW got fingered, Damon had to be sure the body was found, so he tipped off the searchers.
DW's actions are also very puzzling. I don't see his motive. Revenge for Brenda's bar snub? Child predator? Doesn't seem to fit. The blood specks on the jacket are very troubling, however.