Hard to hear this I'm sure...if you can, take even a few minutes away from everything today (mentally, that is). Go for a walk, have lunch with a friend, get a little sun, go to the batting range and smack some baseballs...smell the air and remember that in some way, everything WILL be okay for you over time. You don't know the path or the timing, but things will work out for you if you keep moving forward.
Sometimes we get so busy chasing crazy that we forget to look out the window at the world beyond. Take a minute to remember what life was like a year ago, three years ago...and remember that THAT is what life is. Don't accept current status quo--or slightly improved status quo-- as good enough. Put that in your mind and don't feel guilty for thinking it.
I struggled with "abandoning" XAH when he needed me, and he was good at adding to that feeling to make me think I needed to do more. What I didn't see at the time was that he repeatedly abandoned me emotionally. I wasn't first in his life--alcohol always ranked above me. I couldn't ever be his priority as long as he chose alcohol. They call it a mistress for a reason. He never changed. (Well, until he added more mistresses, lol. Not exactly the change I was hoping for!)
You deserve to be number one. As things develop, please know that in your heart. It's okay to want and need that--to require it of her, and if she's not willing or able in a reasonable amount of time, to step back kindly. Just in case it's lurking there, please don't let guilt in if it creeps up on you when you have fleeting feelings of delaying or stepping back.
I spent 20 years as the "second" with XAH. I found I ended up making me "second" too. It hurts and nobody wins. And it was all my choice.
You've got a lot ahead of you whichever way things go. I just want you to know without a doubt that taking moments, days, or a lifetime for YOU is okay. And you're still a good guy.
Sending prayers and hugs to you today. I know how deeply disappointed you must be feeling. Things may still work out, but I can tell you--you will KNOW it if you see it.