Mila can you see how your husband is trying to make you responsible for his bad choices, because he doesn't want to man up and acknowledge that he has created the mess. For example - saying that if you don't let your in-laws stay it will be your fault for damaging the relationsihp. Excuse me. What region of planet Zog does that family live on?
I could not believe you said 'Bad Mila'. Yes, he got to you, but he meant to. The 'fault' is in reacting, rather than responding, but you were right to say what you did. I think you are frightened of losing your h. And until you let go of that fear he has you where he wants you. Standing for your marriage is not the same as being frightenend of losing your spouse.
The statement about forgiving that he made is part of the MLC script, because they are projecting their deep seated fear of being unforgiveable onto us.
Part of your husband clearly doesn't want to let go, and he knows you want him back. Now there are two courses of action. You either try and stay friends while he goes through his MLC, during which he will likely push every button you have, and you may well end up feeling trashed, This is the DBing approach and it works for some people.
Or you protect yourself at all costs from someone who is essentially not thinking straight, puts himself first, and would sell his grandmother if it suited him. This involves taking a big step back, and letting him have his MLC with minimal support from you, looking after you, and being prepared to let him go fully. And that can hurt. Believe me, I know!
Personally I would write a nice letter to your in laws, and say that you do not feel able to receive them at present, and that they would likely feel uncomfortable too [hand a little responsibility over to them!], but that you would like to see them and perhaps have lunch/dinner somewhere. This will tell you whether or not they just want a free place to stay or really value you . Adultery and separation have casualities, but pretending everything is OK is just crazy to me.
Sorry for the 2 x 4 but you are such a nice person, and your h is such a MLC jerk!