Maybe I have a twisted imagination, but when reading your posts, I think to myself....what happens when your son is 17 and your little one is 7 or 8 years old? What will he be accusing your son of then?
My children are all happy, and seem to be well-adjusted. I wish I hadn't brought this stranger into their lives, but without him, they wouldn't have their sister. I am expecting that we will be able to coexist peacefully for the most part, and occasional conflicts are to be expected in any relationship.
Baby's dad and I had a recent discussion and I think he understands that I'm standing with my kids 100% and as much as I want to be accomodating to him, my kids are my first priority. Hopefully, there will be more trust from here on out.