Hi Carma! Hugs! I've often wondered how you were doing. I am glad to hear you are moving on with your life.
Is Butch's son a teenager or younger? If so, time may help. He may grow out of the extreme judginess.
Why is Butch hiding your relationship from his kids? Is he fearful he could not see them if he was open about seeing you? Job stuff? Is there custody issues or something along those lines?
If there isn't, why is he hiding you? Act like a cheater - hiding things - and his kids will think he is a cheater. Being open and honest will be very painful initially but probably better for him and his kids in the long run. Teaches them that life is fucking complicated. I wonder if that is more about him than his kids. Does he have some shame issues about your relationship? Does he feel he broke you and Sundance up?
As for the falling in love thing, give him some time too. Both of you have had some traumatic, painful, hard stuff to deal with. It takes time to heal from a divorce - give both of you that time. And he may never express love in a way that you recognize. (This is that five love language stuff I blather on about.) He clearly values you - he's stuck around through some very hard times.
And, after a while, if he never wants a relationship in the same way you want, know that you deserve what you want. Learn what you can from your relationship with Butch and move on if need be.