How does he treat you?
That is an important question. My ex was HORRIBLE to me when he was infatuated with OW and was unacceptably disrespectful. But I do regret the destruction of my family.
And I got told off by an older man just the other day who talked of 'stress release' who says he would have given me a big talking to to turn a blind eye.
See, now you know. You can't un-know. 1. This person is not your best friend, he isn't deeply attached (loves you flaws and all), he compartmentalises. You are probably the wife appliance.
But: 2. "he's very attractive and has a good job and I don't work haven't for years" and he loves his children and you live in a nice house and a good lifestyle etc.
So: whether you LTB or not? 1. ALWAYS exists. I am 10 years down the line and I STILL hurt about 1. Still.
But I lost everything about 2.
So my very non pc question is, you have already lost 1. and that is a permanent condition, do you have to lose 2.
I don't know the answer, I am just wondering out loud. Especially if it is just an arrangement.
Whatever you do, be dignified. I wasn't. And it really hurt the children who are now bringing up how the scenes and rows damaged them. They see me as bad as him, which is an injustice that I have to swallow.