Wow.........This is something that I could only dream of. A letter where my wife admitted
the things that she did to ruin our marriage. She NEVER took responsibility. Never apologized for what she did to me and how much she hurt me in the same ways you hurt your ex.
Always the victim. We are in the process of reconciliation but I will NEVER get a letter like you wrote. I have to accept that she just can't do it.
I know one thing , and that maybe in time he will realize what he is letting go.
One thing though , always being willing to take him back puzzles me as to how you can move forward. I can't see how your current boyfriend can be too happy about knowing you would leave him at a moments notice if your ex wanted back with you.