I have looked around, but cannot find a good answer about pets drinking from a pool with salt. How dangerous is this? I have one cat (and countless other critters) that might drink from the pool regularly.
3600ppm salt is not that salty. Most animals around my pool drink the water without issue. Also, mammals like cats & dogs will easily be able to excrete the higher salt levels since they’ll have access to fresh water as well.
Most livestock (and presumably pets) will want some salt. It can be added to an animal's ration to limit intake. Typically, an animal will not consume too much salt and will seek out a water source without so much salt once their needs are fulfilled. The wild horses on the Outer Banks have had access to ocean water, brackish water, and fresh water for centuries. They are able to balance out their salt needs. I would not worry about it.
My pool water typically has over 60ppm borates and I know of another pool owner here that uses 80ppm borates with two small dogs in his pool all day long. If the health of the wild life around my pool is any indication, borates in my pool water is not an issue for them ....