There was another thread on low sodium ideas that you might find of interest (oh wait, there have been a few: here, here, and here, maybe more!)
When I was cooking for a low/no salt family member a while back, we were advised to cut the salt entirely from any recipe, and salt only at the end.
So: no brining, marinating, or anything along those lines — they add more salt than one thinks, but you still have to season later anyway, so… (Apparently even for a normal salt eater that can cut sodium by half - something about how the palate experiences salt on top vs inside.)
Goes against everything we think is necessary to layer flavor, but perspective changes when health concerns are driving the bus.
Good luck to your FIL, and good on you for making an effort to make his food delicious!
