As for the St,Louis Ribs, I haven't tried them so can't speak from experience. I theorize it could have something to do with using Course Salt vs regular salt. Maybe Steven will chime in and provide a solution.
I haven't tried these either, but suspect that you've identified the problem. If kosher salt is substituted with regular salt in the same proportions it would result in too much salt. If memory serves, 1 cup of kosher or sea salt equals about 3/4 cup of regular salt.
And, with this recipe, I wouldn't hold ribs very long before cooking. And I wouldn't put on a thick coating of the rub mixture. That may be the source of having too much pepper.
Just some thoughts....