You may want to read AnotherConfused's story. She is married and her husband is not poly yet has agreed that she can have a bf, as long as she adheres to very specific physical boundaries. She and her bf never have intercourse, and I believe no penetration of any kind.
Well, anyway, her journey is full of insights as she questioned so many things.
Here are two of her threads:
What if polyamory stops working?
Learning to be me