Not sure of all the specifics here but keep in mind that the human body only needs 500mg of sodium / day! as an example here, a 32oz bottle of Gatorade has 110mg/serving and there are 4 servings in a bottle. That makes a total of 440mgs right there and I know I can down a bottle just during one workout. That means I only have 60mg to play with for the rest of the day. Very hard to watch the sodium. I would that using that example that you may not want to use a standard marinade for your steak. you can always look for No-salt as an alternative.
Sorry, but I am not that good with nutrition. Hopefully someone else will jump in here and try to answer some of your questions for you a little better.