All in all you did GREAT! You handled it well and it sounds like it was well received and a productive talk. Give yourself credit because it took a lot of courage today to hand her that letter and express yourself like that in writing.
I can relate to what your W was saying about getting lost in your life and not taking the time to get to know herself. I've learned through this process that I alone allowed that to happen. It wasn't H's fault. And if I continue to do it in the future should we R, it will be my own weakness and inability to care for myself that will allow it to happen, not H at all. Sometimes wives and mothers get wrapped up in the care of their family and put themselves on the back burner but NO ONE told them to do that. They sacrifice themselves and then become resentful that they did it.
Give her lots of space but lots of support. Hopefully, her journey to self discovery will give her the strength I have gained on a similar journey.
I also don't think you blew it by saying you missed sleeping with her. Maybe she didn't want to hear it but you were vulnerable and to me, that's not a bad thing. Perhaps just being more aware of your tendency to over share when you're feeling that way is a good thing to know about yourself. You live and you learn. It's not irreparable.
Congrats on giving a true and heartfelt apology. A great step.
