S.J.
Oh I'm sorry your little guy is going through this! It's the unknown he is fearing. He is asking very legitimate questions and to him, they are big worries. He needs constant reassurance which means he still is not secure in his new environment. Has he made any friends yet? Can he carpool with another child in his class? Is there any way for you to volunteer in his classroom for a few weeks?
When my daughter was in 3rd grade I met a Mom whose daughter was going through this. She didn’t have a car so I offered to take her and her daughter in my car and she stayed and helped when I volunteered. It really helped ease her daughter’s mind. Driving to school with my daughter helped. They would talk and giggle while in the car and walk up to the class together.
Those are the only suggestions I have. I really hope you find something that works!