>>As you don't agree on what H and OW is doing (having an A) and being selfish, I would not act the same way.<<
I personally believe if one is still legally married, then sex with a "husband" is not technically an affair. However, emotionally and physically Olive's husband would be having an "affair" on OW. But from Olive's perspective it's not an affair. He is still her H. Until it's finalized he's legally her husband.
Ourcrisis you are right. OW is not worth paying attention to, but the idea here is to get H out of the house so Olive can have some space to herself. And actually, if she has even a little spark of desire to "save her marriage" (which I don't think she has at this point), this *might* do it. A friend of mine actually did this and the younger, beautiful OW became very jealous of the W, H got tired of OW's possessive jealousy and that relationship ended.
>>let's lay down some rules about how we behave<<
Nice in theory and it makes sense, but I think it's unlikely. D creates a lot of weird situations and reactions. People don't act reasonable or sane when they are in the midst of D.
There is no arriving, ever. It is all a continual becoming.