When using sodium chlorite there are many things to consider. The top 3 include
pH is important not only to the chemical solution you mix up but also needs to be considered for the environment you are introducing the chemicals into. Sodium chlorite is alkaline. When you mix up a dose of Miracle-Mineral-Supplement you end up with an acid.
This is where the environment comes into play. You want to use sodium chlorite in your sinus area. Is your mucous alkaline, acid, or neutral? Also is your current pH the same as a "normal" pH. If your normal nasal mucous is alkaline and has turned acid while fighting an infection, that is important to consider.
This information also helps to figure out if the situation can be addressed by simply using sodium chlorite or if you need to acidify it to stabilize it in the presence of acids.
The next consideration is concentration. When using chemicals you want to use enough to take care of the problem but also want to minimize your chemical exposure. You also need to look at what you can do prior to using chemicals to minimize the amount of chemicals needed.
Water treatment is a good example of this. Filtering and treatment is done prior to disinfecting. By doing that a minimum amount of chemicals are needed to do the disinfection.
The next step in this process is to determine what concentration of chemical is needed to to kill off the pathogen. If you have a concern with staphylococcus aureus for example, you can look up what concentration is needed and find that if you expose the pathogen to a concentration of 30 PPM for 60 seconds you can expect to kill 99.999% of that bacteria. If you are using Miracle-Mineral-Supplement to deal with this bacteria you need quite a bit of dilution. Miracle-Mineral-Supplement starts with 224000 PPM and you need is 30 PPM so dilution is needed.
The next step has to do with the delivery method. Chlorite and chlorine dioxide work when they come into contact with what they are trying to kill. If you don't make contact, they don't work.
This makes the disinfection of a cutting board or counter easy but makes it much more difficult to deal with complex situations like the body. Look at it this way. If you draw a bucket of water from a stream and you want to drink the water, it is reasonable easy to disinfect the water in the bucket. But if you tried to disinfect the rain that was falling that eventually made it to the stream there are too many opportunities for the chemicals to be used up or re-infection to occur to give you any assurance that the water in the bucket has been disinfected.
To get back to your original question salt has little effect on sodium chlorite and if you add 0.3 ml of MMS to 1 liter of water, add your salt, then add enough acid to bring the pH of the solution back to neutral (with my tap water this requires about 0.5 ml of 10% citric acid , if you use distilled water you don't need to add any acid) you will have a great starting place to build from. You will end up with a pH neutral saline solution with about 60 PPM available chlorine dioxide.