I don't know what to say. You are locked into this 8 week commitment, and it is having a very negative effect on you. For the record, you are not a bitch, and you are not fat either. I don't like the way this counseling thing is making you question yourself. Look around you, there are many sexy women who are not thin. It is not necessary to be thin to be sexy. Sexy is in your head, not your body.
As an official, Retrouvaille trained letter writer, I saw problems with the letter you sent him. but it was already sent, so I said nothing about it. If you plan to write him another letter, I would be happy to review it first and take out parts that may seem accusatory. (The method is to not talk about him at all, simply don't use the word "you", especially not as the subject of a sentence.)
But that is past, and it is not the worst transgression within your relationship with your husband. So there is not a need to make a big deal about it. He should not have come into your home and yelled at you in the first place. Funny, how that gets overlooked.
What exercise did they give you for this week? It seems to me that you both need to go back and do the be nice to each other surprises again.