So sorry to read of your situation.

I disagree with the idea that staying married in an abusive situation is somehow benefiting the kids. Divorce is often devastating to kids but if there is abuse, they are growing up thinking that is normal behavior in a marriage.
That said, if you’re afraid to divorce, cheating won’t solve anything. I don’t believe that this guy you’re “in love” with is a good man, to be honest. He knows you’re married and he lacks boundaries, at the very least. I think you should make a choice, either divorce and move forward or don’t divorce but this other man shouldn’t be part of your life until you divorce. It sucks to be in the situation but that’s my advice. Hope you find the courage to get out of your abusive marriage. If it were me, I’d focus on that.