This is a very familiar feeling!
Many examples come to mind during my history with STBXH that relate to your thoughts, S+++for brains.
And all the while during his A and other activities, my needs went unmet as well.
Yet I stayed the course, so to speak and that's a trigger for sure. I had problems with things he did, but tried to work on them, while he went seeking OW and other "activity" outside marriage.
Why do some of us stay the course, while others bail? It seems like there should be other...releases in life, besides As, drugs and things.
Sorry for your pain, you are not alone.
A person is a person, no matter how small. -Dr. Suess
Perserverance and spirit have done wonders in all ages.