Can I caulk over cracked grout (shower floor) as a temporary fix?
I'd suggest you get a small tub of premixed grout, a float, a sponge, and spend an hour fixing the problem. Be sure to remove any loose grout. (Something as simple as a utility knife will work for this. Wear gloves to avoid skinned knuckles.) If you want an even more durable job, score all of the existing grout along the edge of the tile (so 2 cuts per grout line). You'll go through a few utility knife blades like this. Vacuum thoroughly afterwards. Grout is staggeringly easy. Caulk would take you way longer and be a pain to clean up later.