Not only the poor ate lobsters. Everyone did. They were just so cheap back then because there were so many of them, that's why they fed them to inmates. It was considered cheap but good food.

By that logic if you went up in a hot air balloon you'd fall into space as the earth moves away from you. If you're going back in time, your position is going back in time along with the earths position and the position with the rest of the universe.

You'd be moving with the speed of the earth. The same reason when you jump in a plane you don't smack the back of the plane.