You are not completely nutso. If the situation was reversed a parent would have walked out and not come back. In this case the parent was totally out of line on so many counts just with this one incidents. Add in other issues and that just makes it more compelling.

If you do keep this child then no matter what happens in daycare she will blame it on your son so you are no further ahead just delaying a future issue.

I like that you have decided to term. The fact she is pregnant and going to cause disruption in the fall anyways is besides the point. Replace now so you have a new group in place for the fall.