There is absolutely no comparison between you the ow. Sure, she might be younger, but that may get old very quickly when he can't burn the candle at both ends and when the finances get tighter and he can't spend money on all the things that she may want.
You are his wife. The woman who has lived w/him for many years, you know him and what he's thinking, you were his friend, companion, lover and supporter. You are settled, independent and wiser than the ow is. Don't sell yourself short...you have a lot to offer in this day and age. You are the prize and if he's foolish enough to think that he ow loves him, he will be greatly mistaken down the road.
The ow is just a Band-Aid to what ails him right now and that's his ego and yep, acting like a teenager. Don't be foolwed by the way he's acting, i.e., happy as a clam, because he's not. He's searching for something and that search is all about finding himself. The person that was emotionally stunted as a young child/young adult. He's gone back to that time to try to find himself. Hopefully he navigates his crisis well and returns to a mature, self assured man and comes to his senses and realizes what he has lost along the way.
Yes, they do think about us, especially at night. They try very hard to block us out of their memories and they tend to compartmentalize things...but when it's quiet and there is nothing to occupy their minds, that is when the guilt of what they've done to us creeps in. They even keep cards, letters, emails, wrapping paper, etc., when we give them things. They say that they've tossed the stuff away, but many of them don't. They remember more than we think they do, especially around holidays and special events...so, do not for one minute think that he doesn't think about you because he does.
Continue to be you. Be that self assured woman that you are and continue to look after yourself. Don't allow the ow to have space in your head unless she's renting. She's not worth it. Think positive and breathe!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
