My friend sent me a link to this post as it is so close to what happened in my case she thought you might be my ex-husband! My son was the same age as yours when his father left, but we are many more years down the line. I felt compelled to respond out of sorrow and exasperation for your son, although I have no doubt you will disregard what I say as you have the other posters.
Like my son’s father, you appear to live in cloud cuckoo land and have a grandiose idea of yourself. What you need to understand, is that your happiness comes at your son’s expense. You might be able to compartmentalise your life to avoid accepting or minimise what you’ve done, but your son won’t be compliant in that charade.
Your son is 25 and is not stupid. He knows you’re human and will make mistakes and decisions he might not like. But he has a legitimate expectation that you will not make decisions or act in a way that knowingly devastates his life. You say you are happy. How can you be happy when what you have now has lost you your son, caused him pain and disrupted his childhood memories? If you are still happy despite that, then you don’t love your son as a parent should. He knows that. If you don’t act like a parent, how can you expect him to treat or see you like one?
A few things stood out in your post. The first is you saying you tried to explain to your son that you stayed for him. My son’s father said something similar. The decision to stay was yours. Trying to blame a child for being a coward and not speaking up is abhorrent. You have pretty much told him that his childhood family memories are a lie and it’s his fault that is the case. Pretty low on anyone’s standards.
The second is the line that you left his mother and not him. Your son sees himself as part of a family. You walked away from that family and now want to see him on different terms. He was blindsided yet is expected to come to terms with the fact that his family, as he knew it, has gone forever, and it was all a lie anyway. You can leave an unhappy marriage. But as others have already pointed out, you do that in a respectful and measured manner to mitigate any harm to your son and in a way that upholds the integrity of his family memories and allows him a way to navigate forward.
The part where you talk about demonising your wife is really disturbing. Why would you do that to the mother of your own flesh and blood and in the full knowledge that it will upset your son? You say she has refused to talk to you. So what? Surely you expected that would happen if you treated her and your son like sh*t and what do you care if she made you so unhappy anyway? You care because her silence reminds you of your actions and that does not suit your narrative or allow you to manipulate her into bringing your son around to your way of thinking. Your ex-wife has been left to pick up the pieces. You should be grateful that she puts your son first and does her best to make up for you behaving like a man-child. Again, had you left in a decent way and put your son first, things would be very different with your ex-wife, I am sure.
I agree with other posters that you should respect the clear boundary your son has set and leave him be. My son made clear to his father that he did not want to talk to him. I did the same. Despite that he would continuously come to one of us directly. This made things worse. Your son knows the door is open and I suspect your ex-wife will nudge him occasionally as to whether he wants to contact you or not.
As to social media usage, most people keep the things they want to show off about private, even when their joy has not come at the expensive of others. Public bragging posts are done for attention/validation/impression management and sometimes have a sinister motive. I agree with others that it is not helpful if your wife posts things that brag about your new life, not least because they only show a small part of the real story don’t they. It is all very well saying your son should not look, I expect others send them to him (people are nosey) - that is certainly what tended to happen in our case. I don’t know if your wife posts publicly for general validation (look at me and my wonderful life), or if as others suggest, it is for your son or ex-wife’s benefit to make clear she has won the prize. I fail to see how it is not the latter as you wife will know that is how it will be perceived by those that know the truth. I would be astounded if your ex-wife is jealous and thinks of you as a prize – notwithstanding what you did to her and, in your own words, she has shone without you, you have treated the person she loves the most in the world and trusted you would never harm, like a piece of sh*t. Your wife has no need to worry that your ex-wife still wants you given that, trust me. You mention you had a bond that nothing can break. Not sure what planet you live on, but I think you can consider that bond broken beyond repair.
The very fact there is a risk your son might see a post if made public, would be a deterrent for any right-minded person with an ounce of decency as it is blatantly obvious that it would deepen the wedge between you and your son. Showing off is all well and good if you have not caused harm to others. It is incredibly selfish and distasteful to show off in these circumstances. Your apathy about your wife’s posts speaks volumes. It tells your son that you care more about his wife bragging than his feelings and her rubbing salt into the wounds. Actions speak louder than words. You and your wife both know the posts will be harmful.
Eventually the pain may resile and your son come to terms with what has happened. That does not necessarily mean that your relationship will recover though. My son is no longer affected by what his father does, not because he has forgiven him, but because he is past caring and has detached from him as a parent. He sees him as an embarrassing cliché and a jackass, not a father. All very sad and unavoidable.