Definitely more divided today than four years ago. Probably the most since the Civil War. Partly due to the changing demographics, and much of it due to cable news, and social media.
I don't believe we are very many ticks away from taking it to the streets.
We may see some of it after this election.
As for your question about political differences causing a divorce.
I lived with a woman for over ten years, she was a lib. At first I was able to deal with it, but after a few years and the newness of the relationship wore off it became very toxic, until I finally had to break it off.
I thought in time she may eventually come around to my ideological position, but it never happened, and it led to a miserable relationship.
My advice to anyone beginning a relationship with someone from the other side, unless you can be persuaded to change or the other person can be persuaded to change, your ideological differences will eventually become the elephant in the room and you both will be miserable. I would break it off now before you get too involved.