It sounds like they just termed you when they knew you were planning on leaving. There had to be tension and most likely words exchanged for them to KNOW you were looking elsewhere.
When clients are leaving after something happens like this they ALL look the same. They walk the same, talk the same, have the same hand gestures, the same facial expressions, the same voice inflections.
So when you showed them that you were leaving with your response they knew THAT was your signal that you were LOOKING for other arrangments.
That's all they needed. They just want to end it now so nothing else happens. They don't want any more discussions or layers of this.
You missing work isn't going to bother them a bit. It's just time to move on.
And twelve hour days PLUS weekend work???????????? That's a lot of hours away from your child every day.
I hope your child is just in child care eight or nine max a day. If he's in really long hours it would explain almost everything you wrote about his experience.