Hey there! Good questions. My wife and I both come from a very strict fundamentalist Christian background also, and we've both been exploring non-monogamy for about a year. I can definitely relate to the sex-negative past and its affect on things.
The biggest thing for us (and I suspect for everyone regardless of background) was open and frequent communication. We found it was necessary to have regular times of discussing our feelings and thoughts as we moved forward, and always reminding ourselves and each other that both of us could take a break/drop it all together if it was harming our relationship.
One question you'll want to discuss (if you haven't already) is whether or not you'll be telling each other about your adventures in detail. This is a tricky one at times. It can be a turn-on to hear about your wife's explorations (it is for me), and vice versa, but it can also be a bit dicey depending on the mood.
Best resource for us was reading The Ethical Slut . Great, great book on communication and doing things ethically (duh) by all partners involved. Good luck! Any other questions?
The feelings are not going to pass. It is up to you whether you can live with it or whether it is going to break you emotionally/spiritually.
Some books that may help:
Living Two Lives ,
Dear John, I love Jane and
Late Bloomers .
Long thread about gays & lesbians in hetero relationships (lots of sad passages).
You may want to search AL for "marriage" or "married" as that seems to pull up a lot of stories similar to yours. Get an idea of what others have done. What worked for them. What didn't work for them. Some folks are suggesting polyamory or nonmonogamy. That works for some folks, it doesn't work for others. Some folks think they can handle it in the beginning and later find they can't. The 3 major books on this subject are: Opening Up , The Ethical Slut and More Than Two .
You are not alone. You are not the first woman in this situation. You will not be the last.
Would I feel bad about her being with another guy? Not at all. She did have a boyfriend for a few months about a year ago, which I encouraged because they had a good time together.
If she enjoys her time with someone else better than me, that's entirely fine (regardless of gender or sexual identification). I. am. okay. with. that. I want her to be as happy as possible.
If you read my other posts, I talk about this being a journey or a path down broken glass. You're going to learn a lot about yourself during something like this. I was secure before my wife because I know what its like to have nothing left. What's the quote? "Damaged people are dangerous. They know they can survive."
I'd highly recommend The Ethical Slut (https://toptalkedbooks.com/amzn/1587613379) for anyone interested in the non-monogamy lifestyle, and how to handle the related emotions.