Husband is making threats?

I don't know what to do. I separated from my husband 3 months ago and unfortunatley we are still living together for at least another month until the divorce comes through. It was my deicision to divorce him in the first place due to unreasonable behaviour. Although he said the other day that he doesn't care if I have another bf in the future but that as long as the guy has nothing to do with our children. How can any relationship for me work on these grounds? Am petrified that he will try and take custody of all 3 children being under the age of 8 if I move another guy in. I can't stay single for the rest of my life. He hates the thought of another guy bringing them up. I wouldn't want another bf to take their dad's place and my husband will have the kids 2-3 nights a week at his new house when he moves in.