I would simply reply whether you are going to get the kids or not and thank her for letting you know about D.
I have to say that I disagree with Ye's assessment about sex being simply sex.
Reality of life, we all have different preferences. You are not going to meet someone who enjoys the same exact things that you do. Similar, yes. Same, no. However part of every relationship is communication and compromise. So it is possible that you forego some of the things that you like or she partakes in some things she might not like too much for the sake of the relationship.
So unless you selfishly coerced her into doing things that she was adamantly opposed to, I would try to let that guilt go.
As for the threesome thing...again I would let go of the guilt. You asked, she answered, and obviously nothing came of it.
Not knowing how it was approached or the dynamics of your relationship...I can see how that was possible that her feelings were hurt and that IS something that she should have dealt with within herself and by talking to you.
I would recommend examining your motives in asking for sexual things that she might not have liked. I would examine if they are things that you will need in the future, for the future.
One of two things will happen, you will reconcile and have to deal with the issue, or you will meet someone else and have to deal with the issue.
I see so much trying to make each other happy that neither of you was really happy in your posts...which leads me to the thought that communication was not the best.
Learning to be a better listener and a better communicator will benefit you in the long run.
"Acceptance doesn't mean resignation. It means understanding that something is what it is and there's got to be a way through it."--Michael J. Fox