Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...
The other option is just to decide it's past history and forget about it -- but it doesn't sound to me like that works for you.
BUT....
I think you should start the discussion by telling him that "I want to change houses" or "I want to redecorate the bedroom". When he asks why, then explain that you want to make the house/room something for the two of you to be proud of, and that you don't feel good about your home because.....
It will take him a long time to get over it, but when he does, you will both be free of guilt.
In the meantime, burn/destroy/give away anything that reminds you of the affair, e.g. the sheets you slept on, the sofa you cuddled on, etc.
Personally from what Ive read it sounds like the cheating or near cheating are signs that the relationship is troubled. He had the emotional affair and time out, you nearly physically cheated and you both agreed to an "open" relationship because you are both unhappy with the relationship. If all was good this wouldnt be happening. Maybe you did what you did because you felt insecure with your partner after what he did to you or maybe subconsciously to get back at him. I think its the relationship you should be focussing on and not on the cheating which is a symptom, if that makes sense.
Maybe try couple counselling or something to see if you can mend the relationship so you both dont feel the need to go outside it to get your needs met. good luck