I have little to add but ditto to everyone; I think this place is full of lived wisdom!
As for letting him see you mad or angry - that's something I have been working on myself. I don't do that - I can get mad at things but I don't let my H see me mad at him usually. I have been trying to do so since that is being honest with him (as he's being with us, right?).
Writing a letter can be wonderful -- and can also be a catalyst. When my H walked out, he first told me and then handed me a letter he had written repeating everything he had said just in case I hadn't caught it!!!!! I wrote him back one, saying how he wasn't getting out of this easily. Since then, though, R discussions are usually painful. I keep those letters (I kept a copy of the one I gave to him) for... I don't know what. Still, it did allow both of us to say painful things without the pain of having to be pulled into side-alleys of issues. You can always write the letter and then not send it, although giving it to him would maybe be helpful for your own self-preservation and self-esteem.
But as I'm still at the beginning of this journey, just know that I'm following along and sending good thoughts of strength and courage!
