I think you know the answer. But, if you don't...
She has been lying to you for a long, long time. In fact, it appears she's been lying to you from the beginning. She's been stabbing you in the back, and hard, all along. Maybe she does love you. So what? 30 years from now, are you going to be happy with the idea you stayed with a woman who is a chronic liar just because she is great in bed, makes dinner for you, and cleans for you? From my chair, this woman has absolutely no respect for you at all. You are a doormat, and a willing one at that...and all the more reason why she would disrespect you.
Your marriage is on the rocks. It's not just slipping near a rocky shore, with only a minor course correction needed. Your marriage is _hard_ on the rocks.
Swinging is based in honesty, openness, trust, communication, and love. You might have the latter of those, but none of the others. Swinging isn't something you do to fix your marriage. I guarantee you that introducing swinging into this marriage will do nothing but cause more harm. As is said here many times, swinging magnifies what it finds. In your case, what it will find is a deeply troubled marriage that needs serious help. This will only be magnified, and the problems will be worse.
This idea that you can't look at her laptop or phone is just childish. Absolutely childish. No spouse should ever feel they are in a position where if they look at their spouse's phone, they are going to be in trouble. My wife has access to everything, as I do with her. It's an afterthought. It wasn't some moment where we agreed to do that. It was just normal. I rarely look at my wife's phone. Sometimes I do because I hear something come in and she's distracted, or occupied. So, I'm doing it to help her. Same goes for her. There's no distrust. Everything is 100% open. We share each other's deepest thoughts, and are deeply intertwined in each other. You have a "us vs. them" marriage, with clearly divided camps.
Your marriage is failing. Swinging won't fix it. Get help. I'm not saying this to insult you in any respect. I'm saying it to help you. Your marriage needs help. Get it.