Welcome to Websleuths, Ruthie!
I think that anything you asked above is possible. At this point, almost anything in the world is possible.
I too have been very concerned about how dad is acting. I watched from day one and at first he seemed very distant and cold to DB. He didn't hug her or comfort her and always looked down. It seemed like he was mad at her. I have no idea if this is because he knows that she did something or because that's just his demeanor. Since none of us know how he acts in real life, it's really just speculation.
I don't know the answer to the DNA part. I believe that DNA can match a person or not match. However, I am pretty sure that LE took a sample of the area that the dog hit on to compare to Lisa's DNA.
Again, welcome here and post often. We may disagree with others here, but I believe that all of our hearts are in the right place.