Is it legal for a repo man to open your garage and threaten to block you on the street and tow with you and kids inside?

No. In order for a person to repo a vehicle, it has to be visible from the street, and it can't be occupied. This would be an invasion of privacy. NO WAY!!! First, he cannot go into your garage. He cannot block you in. He cannot tow the car with anyone inside. If this was done, call the police and an attorney. File charges and sue the idiot. You will win.