Hi 76, welcome to this forum. Sorry you are here but you will find lots of people who understand what you are going through.
Your story sounds like a struggle. It must have been so difficult for you.
Of course it is hard to say just reading your account but it does sound like more is going on than your wife is telling you. Is she still having an affair with this guy? Is she being honest? If she's not actually in contact with him, is she still obsessed with him? I'm afraid the answer to the last question at least is yes, probably.
Is it odd that she is more affectionate after a blow out? No. She is afraid to be without you. But she isn't able to/doesn't want to give you what you need either.
Like all the vets tell the newbies on here, the best thing you can do now is focus on YOU. Forget her and her struggles and your relationship problems for now and start looking at yourself. What about yourself can you improve?
- Is there something that you've always wanted to improve about yourself? - What does your wife complain about that you do or don't do? Can you work on changing without talking about it? (do the laundry, clean the house, make dinner, make more money, be on time... whatever it might be) - Are there hobbies or interests you've always wanted to take up? Or something you love that you stopped doing? (sports, art, activities, friends.. anything)
If she's in the midst of an affair, whether physical or emotional, she's going to have to decide to get over it on her own. The more you try to get in the middle of it while being there for her, the worse it will be. It sounds like she doesn't want to lose you or is simply afraid to be on her own. She's going to have to realize eventually that she has to be 100% in the relationship or she will lose you. The best way you can get that realization rolling is to focus on YOU.