((ChipHazard))
First of all welcome to SR. I'm glad you are here but sorry for the circumstances.
I have a question for you, As much as your son and you love this man, is it the example that you want your son to have? Even if you think your son doesn't "know", he does. He may not indicate to you that he knows, but believe me, he knows.
What about you? You have done good for yourself, you have been strong and faced parenthood alone and have done a pretty darn good job, so what do you really want to do now? I know that sounds like an easy question, but it isn't. I know you have mixed feelings. But it really comes down to a decision.
Sending you lots of hugs Prayers and understanding.
B