Welcome to the forums.
I'm a Christian, too, and when my dear Hubby started talking about wanting to transition to poly, naturally that conflicted with traditional Christian teachings. In regards to adultery especially.
I found the book Divine Sex: Liberating Sex from Religious Tradition to be very eye-opening and informative. Perhaps you might find it interesting and enlightening as well.
Best of luck to all three of you. Be blessed, SisterWoman, be a blessing to others.