Do I tell him all I know?

[MrBond]

"He acts like the good father, "

Is he a good father? You can't base it off of his A because that's an issue between you and him. Is he a good father to your children?

What marital issues were there in your M? Not saying that his A is justified, but there's usually some condition in the M that might have planted the seeds for it.

Have you read DB or DR? If not, that is an absolute must if you want to continue here and understand the process.