Jenn, infidelity is a VERY hard thing to deal with but when D is involved, its even harder. It is important that you be clear and non-flexible when it comes to having your needs met in regards to healing from this. He erred....therefore he must do what is necessary to right the wrong, regardless of how uncomfortable it makes him feel. If he cannot do that for you, then you really have to consider why you are accepting less.

It is common for the offending D partner to try to make you share the blame for their choice. Don't allow it. YOU did not cause this. No matter what he says. The situation is his to own. So never conceed to accept responsiblity.

As for the dinner party issue, I don't think you need to feel sorry for that either. He was clearly being rude by staying when uninvited. His behavior in social situations reflects on you as well. So you had every right to encourage him to leave as planned. Although try to do so in a "non snarky" way. You have more power when precise and controlled. Keep your poise and you will find he responds better. Plus then he won't have a reason to blame you for his "feelings" like he did. His childish rant about going from a 1 to an 8 to a 2. That was all done to manipulate you into taking the blame for his lapse of judgement. If you accept that behavior you enable him to do it again and again and again.