There is no need to compare your situation to others or trivialize your hurt. You have every right to feel this pain though I am sorry you are having to go through this.
Your WH should get himself into IC to figure out why he is looking for a fantasy relationship. Why is he idealizing an old gf? How can he start to appreciate that life is about the daily ins and outs? How can he learn to be content with what he has?
It is certainly possible that there was more to his reconnecting with this woman than you know. But I think you have good signs from him so far.
Give yourself time. A useful saying here is 'actions, not words'. His actions will show you where his heart and mind are.