You are right to be cautious. I appreciate how you are trying to deal with this situation sensitively. On the face of it, though unusual, this situation makes a kind of sense. Your daughter is with a man who was raised by this man. It makes sense to me that you and your daughter are attracted to similar qualities that the two men possess. Since the man and his ex have not been together for 30 years, it’s likely he has resolved his own divorce and is ready for a relationship.
However, there are two red flags in your letter. One is your history of failed relationships. Unless you have done some meaningful therapeutic work, you may be overlooking some red flags of your own. Further, you reported that you have been lonely since the loss of your mother 7 years ago. That suggests that your grief is unresolved. Your judgment may be clouded because you are aching for someone to fill that emotional hole in your life. However wonderful he is, he won’t fill the hole left by your mother.
For those reasons, if you want this relationship to have a chance, I do think a few sessions with a therapist is in order. You need to resolve your grief around the loss of your mom. And you need to be sure you aren’t finding another repeat of your mistaken choices of men.
If you do that and you and the therapist agree that you are truly available for love by a different kind of guy, by all means explore what could be a promising match.
I wish you well.