Eruvin 35: If You Come to Move It, Move It

A detour: When someone becomes a "zav" and is impure, that impurity can be transferred to an item simply by moving the item. But only if it's a kli, utensil, not if it's a tent that moves. And depending on what makes it move. Back to Eruvin: What happens if your eruv techumin is no longer available to be an eruv - if it rolls outside of the techum, if it's been destroyed, or rendered impure... Plus: The eruv meal - symbolic or your main food?