It's funny. I've been reading your sitch and it reminds me of where I've been and where my marriage was after H's first affair. That was over 10 years ago. It occurred after our second child was born. Looking back I know we had many years of just kind of plodding along in the marriage, trying to "fix it," but never really feeling connected again.
Over the years I know we both thought of leaving. I had read a book once about a character married to a doctor who leaves her home, travels to another state, and then quietly starts a new life there. She gets an apartment, a simple job, and even has a romance! I never forgot that book and I used to dream about doing the same thing. Just chucking everything and starting a new life elsewhere. But, I didn't do it, even through I've never forgotten that book. Someday I would like to have an adventure like that. (Although I did have some fun and adventure during the D!) By the way, at the end of that book the character ends up going back to her home and being with her husband. There was no drama to it. She just kind of decides it's time to go back to her life. I think she felt it was comfortable and where she belonged.
I wish I had some good advice for you. I think it's a very good idea that you are going back to school. Interestingly, that had been my plan too. I had figured once the kids were a little more independent I'd go back to school to brush up on my education, maybe get an extra degree or credential... and then go have MY adventure.
But my husband jumped the gun on me!
There is no arriving, ever. It is all a continual becoming.