Hi Totallylost.
I could understand how you felt after your husband telling you that he wants his freedom and his gf thinks that she having an upper hand in the relationship.
If i were you, I will definitely sue my cheating husband since he is the one trying to be young and free after so long. There should be consequences for every actions that he take. The problem that he taking such stand with you, maybe he knows that you will let him win and wait for him.
In fact, humans are very strange beings (no offence), they will not treasure what they have now and take things for granted. Once the treasured things are missing from their life, they will come chasing after it again. To me, show a strong side to your cheating husband. Prove to him that you can live or even live better without him. When things are not rosy over the other side, he will come crawling back to you.
Besides, you have 2 kids. You can choose your lifelong partner, but they cant choose their parents. Have more time with your children, definitely better than seeing your cheating husband any time.
Ya, you will having lonely moments, self-pity, convincing yourself to just wait for him to come back. Is he worth the wait? It is a phase to grow out of so have the patience and the courage. It is never easy to be alone again. But give yourself some times. Focus your life on other areas. No point crying over spilt milk. Upgrade your market value, have confidence in yourself.
AS for the gf, just ignore her. She probably thinks that your cheating husband will divorce and marry her. Well, from what i know, once a cat taste the fish, it always want to eat the fish again. unless it turn vegan. Haha..