Back to the Future question

Three things have always stuck with me about these films:

1. Biff tried to rape Lorraine back in 1955. Even though George laid him out and established dominance, I still wonder why of all the people out there, he would choose the guy who tried to nail his wife at the dance.

2. If, in the new timeline, George is rich and successful and now rolls in a BMW, why would he still choose to live in that shitty house underneath the power lines?

3. Marty had a considerable amount of interaction with Biff, George and Lorraine in 1955. Assuming he wasn't conceived until roughly 1967 or 1968, it's obvious he wasn't the offspring of an affair between "Calvin Klein" and Lorraine. Do George and Lorraine never question why their son looks a lot like the kid they knew 30 years ago? Sure, he was there barely a week, but it's still very obvious.