I hear you. As for the backslide, a little one won't kill you. Learn from it and then turn it into an opportunity. The next time you have an interaction with your H, use your mistakes as a platform for showing how you've grown.
For example, apologize for the last exchange, tell him you wrote your letter to share your thoughts and feelings with him and that you'd hoped he would do so in return. Tell him when he didn't respond in kind you felt hurt, but that you realize expecting him to react in some preconceived way was unreasonable and you are not proud of how you reacted.
You'll have to swallow hard to get it out, but it does you no harm and proves that you are capable of being painfully objective about your own shortcomings (I'm sure he's already aware of your ability to be objective about his).
It's not a miracle cure, but it's a baby step in the right direction. I'm sending best wishes your way. Patience and wisdom to you.
