Two crates are fine. The idea is that dogs won't mess up their den.

I think putting the poo in the rock yard & taking her out is a good idea. It might help her connect the dots.

If you don't feed twice a day, I would start. Make the morning meal larger so it has time to process through.

I actually like prong collars a lot more than slip collars, btw. Can't strangle themselves on prongs. Much less trachea injury too.