I have not yet had time to read all your sitch, but I have seen the RobX "let them go" approach work very effectively. HOWEVER, do NOT do it via a letter/email/text; it MUST be done in person, while looking her square in the eye.
Also, if you add what you're wanting to add "this isn't what I want") you might as well not even bother, as that pretty much negates all of the rest of it. You want to come across as "this wasn't what I ORIGINALLY wanted, but now I realize that this isn't working for me either and I value myself too much to stay with someone who doesn't want to be with me," and "I see that now. "
Otherwise, she will see thru this as just another tactic to get her back. The whole key to this approach is for her to sense that "oh my, I've gone too far ... u-turn is moving on!"
