Unless you have a medical condition and your doctor is limiting your salt, I would not worry about salt in backpack food. For me it is the taste. I cannot stand over-salted food. I rather have bland food and add salt, to my taste.

In general I try to get 18-20% of my calories as protein. Since I often fish, I do not get too worried about a lot of protein in my dry food. The longer the trip the more important to get sufficient protein. I doubt low protein would cause problems for a 2-5 day trip. Protein helps you feel full longer, which is good for a long night's sleep. I try to get most of my protein at the evening meal.