Taking a break from being physical with a lover is not the worst thing that could happen to a person. Not to be dismissive of what you're feeling in the least, but... your wife will be fine, the other couple will be fine, they have each other to fall back on and you and she also have each other, no one is alone. This *is* a rough situation, and she clearly loves you very much to give you this, but you feeling like you're a terrible person will not make this better. She accepted your gift of trying to make it work, now you must accept her gift of suspending operations (so to speak) and focus on the work of rebuilding your marriage!
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.