I don't know if Calystra is still around...but way back when, she advised us to tell our WA that we forgive them unconditionally. I did the same thing you did in that letter...I apologized for what I saw as my mistakes and I told him I completely forgave him for everything.
Even today, my husband holds a lot of guilt over many things. I sincerely believe that my apology touched his heart...and my forgiveness helped him not be as afraid to come back to me.
As for the dance of contact over long distance...I don't know much about your situation...
So, will just cheat and ask you some questions!
How does he respond to contact from you? Does length of time between contact make a difference in his response?
For my husband, if I called him more than 1 a week, I wouldn't get a favorable response. In the begining of my DBing, I think I had to go 2 weeks between contacts to get a favorable response...but as things improved was able to initiate contact once a week.
BUT!! I do think it's much better for him to contact you. I understand needing to touch base for your own sanity...believe me! But the way I saw it...each time he called me, he knew he was doing it of his own free will...because he WANTED to. And him realizing that he wanted to call me helped him come home.