IB there is nothing wrong with you. What you are feeling is normal. This guy was your life, and now he is behaving as badly as my xh, and that is something.
Clearly it is up to your daughter but when my son got married he made it clear to xh that OW wasn't welcome, and a good friend of mine [ex policeman] was all lined up to march her out if he showed up with her. She didn't show up, but they have either lost all sense of what is appropriate, or they simply do not care a straw for anyone else.
It is unacceptable to turn up at a wedding with an uninvited guest, and it may be that someone will have to spell it out to xh that he comes alone or not at all. Even without xh my son's wedding was stressful enough with a MLCer even there! But it is your xh's choice imho, to stay away or come without OW. It is not your daughter's obligation, if she really doesn't want OW to be present, for her to be there.
It takes a long time to 'get over' this type of hurt humiliation and betrayal by someone we loved and trusted. Was your xh always an insensitive type of person or is this new and MLC type behaviour?
Over 6years post bomb, and nearly 7 years significant behavour change, I am pretty much OK, and happy to be me most of the time. Even so I sometimes see other couples and wonder where my life went? But it isn't normal to move on quickly in emotional terms, after a long and happy marriage. I wonder about people who appear to do this, whether they have really healed.
