Hi PE -
I don't post here very often, but had to reply to your post -
"All he wants he says is just the relationship and no hassles."
This is just another way of saying he wants you for the sex and he wants you there for him when he wants you, but he doesn't want the "bother" of a true relationship and the heck with what YOU want. Of course he doesn't want any hassles - who does?? As long as things are going the way he wants, great. If not, it's your fault and you're being mean. You're right when you say he's playing with your head - and he's going to drag you down even more the longer you allow it to continue.
" Now he is trying to involve me with his son, who needs help with tutoring.I don't think he will leave his wife."
You're right - he's not going to leave his wife. He can hint at it all he wants, but there's a 99.9% chance that it's not going to happen. This is just another way of keeping you where he wants you. If he wants a tutor for his son - tell him to go out and hire one.
"This is exhausting, and interferes with my work. I want to be happy. It's odd, but I miss him even though we fight so much."
And the longer it continues, the more exhausting it will become and you will be further away from being happy. You miss him because right now, to you, even negative attention is better than no attention. Staying in this affair with the hopes of something more is not the way to happiness.
"Do you have any ideas on how to be strong?"
You need to take the time to be alone with yourself and to take the time for introspection. Your abusive marriage of 25 yrs ended recently and now you've jumped into what sounds like an emotionally abusive affair looking for validation, companionship, attention, etc. You need to take the time to allow yourself to be alone, to get to know yourself, and be happy in your own skin. You also need to figure out why you're getting involved in these abusive relationships. Happiness, validation, etc. can't come from the outside - these things have to start from within and you have to believe that you deserve more and that nobody has the right to physically or emotionally abuse you - ever.
How do you do it? Well, the simple answer is "You just do". YOU are the only thing that YOU have complete control over. You cannot control anyone else's actions. You cannot control how other people treat you. But you CAN control your actions and to a large extent, your thoughts. If you need the help of a church and your current church does not believe in divorce, find a new church. Maybe a non-denominational church - there are millions of church-going divorced people out there. Find support groups such as this one online and read all you can. Find things that you like to do and do them to take your mind off of your divorce, affair, etc. Concentrate on the realization that you are worthwhile just because you're you and you don't need a man or a relationship to validate you.