Not having read your situation in whole, is the letter a good idea? I ask if it is a 180 for you? Does she respond well to letters? Usually the given around here is not to write them or if you do write them, don't send them.
Now, if you really do plan on sending it. I would say, Drop this line: except the Sun evening in CA. and the drive home on Monday, when I was being a total ass as usual.
Also, when you list some of the things that she said you did in the marriage that hurt her, I would leave out the there may even be others, but those are the ones you told me about line. and the part where you remember them but they never stood out in your mind. I would say that you remember them but take out the part where it didn't stand out in your mind.
The part where you tell her she is doing great at becoming independent and the list that follows is a little condescending. Like a parent talking to a child. I would drop that.
