HI B-V2, I'm a "Mrs. Fix-It" so I am familiar with this issue. And actually, I'm finding it liberating in many ways to not feel responsible for his problems anymore. Certainly, in my next relationship (whether with him or someone new) I plan to avoid trying to "fix" or "rescue" or "help" others unless they explicitly ask for it. This is an opportunity for growth.
I hear you about wanting to just connect with her, and about writing a letter. I am struggling today with wanting to connect with H to get some clarity about the direction of our R, but I know that is verboten. Some days it's all I can do not to think about the problem as something I want to "fix." Instead, I need to work on fixing myself, and that takes introspection (which you are doing), and GAL, and time.
Being patient and allowing time to take its course is the hard part. I feel for you. Hang in there.
M: 43 H: 39 D: 14 Married 15 Together 16 BD: 6/2014 S: 8/2014 OW revealed 10/2014 Instigated dissolution 12/2014, in progress So over it!