My theory on the Lisa, Dutch, Neville triangle relationship.

Dutch might have, voluntarily, taken a back seat to Neville because Neville was the the one who created and had the vaccine.

He might have been tapping Lisa, but backed off, gracefully, letting Neville play his hand with her because of the serum.

Dutch let Neville have his way because Neville was much smarter, and saved himself, and now he can save Dutch and the others.

At the end, Dutch was not too broken up about Neville's death. He made no attempt to try and help him or console him. He basically grabbed the vaccine or syrum out of his hand, and was quite cool about Neville at that point.

Also, while Lisa was strong, she was weak and vulnerable - she succumbs to the family, so maybe Dutch was playing all sides, so he could get the vaccine and survive.

As for the teeny boppersm, they were quite young, even for Dutch.