Hi RC, Welcome although as always I am sorry you are here. You will find a wealth of information and support through these boards, and you were already visited by grasshopper, one of the masters in my book, so you are in good hands.
Regarding the snooping, it becomes obsessive and can control your mind. You just need to stop, cold turkey. It is a weird thing, the more I have snooped, the more I have wanted to snoop. And not one thing I have ever found out by snooping has really helped me. In fact, it has me become a suspicious character instead of a trustworthy one. I want my H to tell me when he is ready to tell me - THAT would be satisfying. The occasional snooping, with partial information taken out of context, does nothing but make me crazy and more suspicious. It never solves anything. So just stop.
Divorce Remedy is really good. Read it cover to cover, highlight and dog ear, and return again and again. Take on the exercises. Creating a Solutions Journal has really helped me. My H moved out in January (per my request) as he chose at that time to continue the A and told me our R was over because he "didn't love me" and "had to follow his heart". This was before I read DR. We have made a lot of progress since then, although it ain't close to over yet. But I believe to the bottom of my heart that Michele's techniques work, if you really take on your own personal growth and aren't just trying to do techniques to get a result you want without personal introspection.
This is a really good place to get support. Make sure to come here often and seek us out. If you are truly committed to your marriage, there is hope. But your actions are very important right now.
Regarding your daughters, I feel it is appropriate to set healthy boundaries around contact with an OM. If you can neurtalize your emotions, you might be able to have a conversation where you tell your W that you would prefer to keep the girls for the weekend if she will be seeing OM, and although you would prefer that she does not continue to see him, it is her choice about her time with him - but you do have the right to particpate in the decisions that relate to your daughters' well being. I would encourage you to be clear around the healthy boundaries for your girls now, as having them stay in a hotel room alone while mommy is in another room somewhere else in the hotel, is not safe for them. Others may have a different take on what should be said. But you have a responsibility as a parent to protect and look after your children, and I would encourage you to have that conversation about the care for your girls' well being, and get some agreement about that with your W as a bottom line requirement.
The only trouble with boundaries is that you have to be willing to enforce them, or you will become weak in your W's eyes and that will hurt your situation. For example, you can ask your W not to see OM, but you can't demand it unless you are prepared to follow through 100% on whatever consequence would occur. In your case, because your W has said she is not going to end it, you should stop all requests or expressions of what you want. This is outlined in DR. And especially don't make demands - no ultimatums - unless it is a make it or break it issue for you and you are 100% prepared to back it up with consistent action no matter what.
Good luck. Keep checking in and let us know how you are doing. It can be a long haul, but I am finding many rewards now that a few months have gone by. I remember how awful I felt in the beginning. Please hang in there, and do some things that you like and that are good for you ASAP.
PositivelyListening ************************************** When one door of happiness closes, another one opens; but often we look so long at the closed door that we do not see the one which has been opened for us. - Helen Keller