That's a good question. I was worried about kidney damage with so much salt too... but a lot of people find that the salt loading doesn't affect them negatively. It's supposed to help if someone experiences headaches and stuff from bromide detox. In my experience, the salt push didn't have any affect in the beginning... then one day I had gotten a headache from taking ALA supplements and the salt push took it away and I was peeing a lot.
Maybe go with what your body is telling you. If you have a headache or feel off, try a salt push. I only do them once or twice a week as a precaution type of thing... just incase I am detoxing but symptoms aren't enough to make me realize. I can't stand the taste of it so I'll put like a quarter - half tsp in an ounce of water, slam it down and then fill my cup with water and drink that down fast.
Its weird how the whole thing works. My detox was through my lungs. The first week on Iodine I got hit with what felt like a chest cold, but then it went away.
Most people get headaches.

Pink Himalayan salt has less sodium than table salt so you can take more of it but it is also healthier than table salt .. has minerals that our body needs. Look up the book salt your way to health. I had high blood pressure and was on medications when I started the keto way of eating and have been drinking pink Himalayan salt water 2 to 3 times a day for almost a year... No high blood pressure and no meds.