L.F.
M.,
You have to protect YOUR babies at all times. Do not hesitate to call the police or 911 immediately when he is out of control. He should have never had the opportunity to hurt your 3 month old or even attempt to kick your 4 year old daughter. That is outrageous and to think that you are afraid to call the cops? Please, protect your kids and push your fears aside. This man is dangerous. Whether he is family or not, mental health issues or not, he is a danger to you, your children and society. Please protect your kids and call the police when he gets out of hand. In the mean time, start searching for another place for you to live. Or even better, find him a home that will take him and a place where he will be safe from hurting himself or others.
As for MIL, if she won't call the police---You need to. Your children are more important than her feelings about it or anyone else's. Its time to stand up for your children and show them this isn't right and you WONT tolerate it ANYMORE! Best wishes and I hope you get the help that your family needs.
M