How can my husband be so retarded and think it will blow over when u cheat on our couch?

Found out a couple weeks ago that my loving,devoted husband brought a dirty chick home and had unprotected sex on our couch while I was at work.This retard has NO idea why I'm so upset and hurt.Feels "Sorry,I made a mistake and it was only once" make it all better.I want out of this marriage and he thinks I'm acting "crazy".If I was crazy,him and the couch would be GONE.Don't want to be bothered with him but he will not leave.Its too convenient.Already went to the court and started what I need to get the whole separation process started.I know I sound cold but its easier than showing the utter devastation after being loyal and FAITHFUL for ten long years.Never getting married again.In trying to cover up his affair he became abusive so no, making up is not an option.