Clemson, I am so sorry you find yourself here. I know you are in a terribly difficult place and there are no quick solutions.
In regards to the affair fizzling out after 6 mos, maybe it does and maybe it doesn't. I know several people who have married affair partners so I wouldn't put much stock in that figure. I also wouldn't worry what the family thinks. They aren't in the marriage.
Take a step back and think about what you really want to do. You don't have to decide right now. And about 18% of people who divorce remarry. Maybe you would be in the 18% or maybe the 82%. Doesn't matter right now.
Hang in there. It does get much better!!!
3 kids BD 12/15/13 (IDKIILY. ) Rope dropped Cirque du Soleil style D final 9-9-14 "Some people are born on 3rd base and go through life thinking they hit a triple." Barry Switzer