If I were in your shoes, I would stay in the UK with support and shelter and basic necessities. This is what is best for a child.

No one can live comfortably or feasibly in a car in the winter, in Massachusetts. Temps drop below 0. You will freeze to death, literally. It is not fair to you or your child if you are living in a car without any necessities or funds to get those necessities.

Once your child reaches school age, teachers and school personnel will most likely contact DCF if they find out the child is living in a car in the winter. Although it is not your fault, the cold temps and absence of basic necessities at home (a bed, shower, food, etc), school personnel are required by law to file with DCF.