OP,
You poor pet.
So glad your mother is there to support you and your MIL is a good woman too.
There is a particular type of scum that is unfaithful whilst his wife is healing from a tough birth.
A very specific type of scum.
Don't waste your time trying to fix this, he really isn't worth it.
Funny about the golf.
Some long years ago my friend at work was very upset to learn her husband had given cover for his colleague who was having some fling and it was also via golf.
She wasn't married long and adored her husband but was genuinely devastated that he was prepared to be involved in such shabby behaviour.
It was a really huge deal for her and she said it changed how she saw him and really affected her respect for him.
He swore he didn't give it much thought when he said yes, but she thought it made a lie of their wedding vows and they weren't married a year.
It really caused huge drama.
He went back to his colleague and rescinded the "cover" and they slowly healed.
He was on very thin ice.
I would be seriously unimpressed if my husband did it.
When we were dating we would go out with a rugby friend of his and his lovely wife.
The boys went on a rugby tour and he was unfaithful to his wife several times in front of the team.
My boyfriend at the time came back and told me how uncomfortable it made him feel as he really liked his wife,
He let the friendship drift and we didn't socialise as couples again.
Same git was seen giving his card on a plane to an air hostess 🙄, vain twat.
30 years on they are still married.
I reckon she knew well what he was like.