I'm not fully up to speed on your sitch Brian, but will post some comment here:
While we don't generally encourage letter writing to the WAS, in your case I feel what you wrote was very appropriate.
The only thing that struck me was at the end, how you indicated that the two of you might write / contact friends. Basically, that may have come across as pushing your will on her. Even if you both agreed to write a joint letter, she will likely communicate with people her personal perspective outside of the letter. Nothing you can do about that.
Your T sounds on the mark. From what you've written, there's not much to add around that.
So really, the only things to "pick on" and it's generally not something we encourage, to mind read or analyze our spouses words and actions...
It is just to point out that your W made a comment that she wished you had become this guy doing great things before she chose out. And that she wants to remain friends...
The first is projection, indicating that it was up to you to change her mind and make her feel good about staying. It will be up to her to realize (or not) that she made her choice and if she failed to see that you could and would become someone she could find attractive... well, we all enter into M's with faith... ok, sometimes it's hope and expectations disguised as faith... but our intentions are usually good...
The part about remaining friends can sometimes be interpreted as attempts to keep the LBS strung along with (false) hope...
We choose our friends how and when we choose them... I'm on the "People come into our lives for a reason, a season, or a lifetime" right now, and only time will tell which of those your R with you W will be...
Anyone can make a "pact" to be BFFs... but what if you fall away from that friendship... then you've gone back on your word...
IMHO, the best response to a request for continued friendship is a simple, "We'll take things one day at a time."
As far as the D, your decision is appropriate. Not so much drag it on, but let her do the work, and do only the work you are requested to do and only within the alloted time frame.
Just do not do it as a tactic in the hopes your W will change her mind. Just use the time to become the best person you can, with the skills and strength to take on the future, whether or not the D goes through, or not...
