> I have my own inner thoughts but they can be rather dark, and need extensive filtering before being presented to the world at large
This really sounds like a good thing to reality check with a therapist! Non-judgmental listening is a core piece of the service they provide.
I've had similar feelings in the past. Having things you don't feel you can share will make you feel isolated. Saying these things out loud to someone in and of itself can be a load off. And I strongly suspect these things you're suppressing aren't as bad as you think.
It's telling that your response has nothing bad to say about your wife. The issues you raised are really, really not going to be solved by leaving her.
When I'm unhappy in a relationship being single feels like freedom. But a breakup is trauma. During mine I went through hell, my entire being was be screaming at me that I'd made the worst mistake of my life. The loneliness was profound. Self esteem plummeted. My ex-girlfriend went through hell too.
As it happens, my breakup needed to happen - I want a family, my ex-gf could not commit to having one with me. I'm on the other side now and feel good about the decision. But I still miss her all the time. And this was a relationship of only a few years.
Lastly, on my friends with dads who have divorced their mom in his 50's - this decision will permanently change your relationship with your children. One doesn't talk to his dad at all, the other tolerates but no longer respects his dad. Are those scenarios possible?
Good luck. Maybe it is that you have to leave your wife. But do your due diligence that this is the case. It's a button you can't unpress.