Why is the caulk cracking and the toilet rocking?
You don't have a caulking problem, you have a structural one. The walls and floor shouldn't be moving so much that caulk cracks. And caulk isn't an adhesive for holding up the soap dish or towel bar. Finally, a rocking toilet indicates the floor either wasn't properly leveled or that it's not structurally sound. If these are the issues you are noticing, then you can be sure that there are a lot more serious problems you aren't seeing.

You don't want that contractor back in your house to fix these problems. You want to sue them for gross negligence and to get someone that knows what they are doing to come in and fix it. To fix it right likely requires gutting your bathroom all over again and starting over from scratch.