Please bear with this to the end.
Assuming this situation is real, it should be a wake up call for you. I’m not sure where to even start... there are so many red flags / issues.
Knowing you work with kids, why on earth did you think it was acceptable to essentially move in with a widower AND HIS CHILDREN after such a short space of time ? They will all be grieving still, particularly the kids, and do not need this kind of disruption. I would not even introduce a new person to my kids before a least a year if I was to separate from their father, and when you have children dealing with their mothers death it’s even worse.
You’ve not answered any details of how you got pregnant - and by that I mean we’re you deliberately trying (either with / without his knowledge), a contraception failure or just careless ? To be honest any of these are stupid with someone you’ve just met, let alone someone in his circumstances.
You also seem unprepared for dealing with a relationship with a man with children, let alone a widower dealing with children with understandable mental health issues. Your comments show you are in no way ready / suited for a step mother type role. “Dead wife’s kids” was a particularly horrid comment that jumped out at me.
Behaving hysterically when he’s looking after his children rather than driving to meet you for dinner ? You should be ashamed of that, hormones or not - it’s the one thing you’ve said about him that’s decent !
I think you need to take a long, hard look at how your own actions have brought you here so you do not make the same mistakes again.
HOWEVER...
He has clearly reacted very badly to your pregnancy and I agree he was probably telling you what you wanted to hear previously to get free childcare and sex on tap. And you fell for it.
To have already had one long term relationship move in and fail before moving you in in such a short space of time is truly awful. Did you know about this ? If so, why did you think it was ok ?
He is clearly not a great guy for you. You will be better off without him and need to learn from this and slow down in the future. You might not have been so careful thinking about the effect of your actions on his kids, but you will have to be careful with your own child in the future.
In your circumstances and with your plans to have a baby anyway you've had a lucky escape. Imagine if you did not want a baby...
BUT you've got what you wanted... you’ve got a baby without the effort and expense of IVF. Congratulations (that’s not sarcastic by the way).
Cynically, you've also now got someone on the hook for maintenance payments (well payed if that was planned).
He made the baby with you, so it is correct he supports the child. You’ll also need to work out how to co-parent together (assuming he wants to). Concentrate on the child and doing what is best for him / her.
Good luck.