Sorry but the "potato trick" is a kitchen myth which has been dispelled over and over again by food scientists.
A potato does not selectively soak up only salt. It's just a sponge, soaking up some of the liquid.
Robert Wolke says " There was no detectable difference whatsoever in the salt water before and after being simmered with potato.
That is, the potato did not lower the concentration of salt at all, either in the one-teaspoon-per-quart sample or in the one-tablespoon-per quart sample. The potato treatment just doesn't work. Period."
Read more here
The only way to save a salty soup or sauce is to dilute the liquid or add more of the nonsalty ingredients.
Also, sea salt isn't saltier than table salt or kosher salt. All salt is equally salty.
What is different is the size of the salt crystals. The larger the crystal, the less salt per volume in a measuring unit. Kosher salt's crystals are larger than table salt's, thus you need more kosher salt to achieve the saltiness of one teaspoon of table salt. So it depends on crystal size,