For starters, Norton, GE, Kenmore, Sears, Polar Star are all the same units, but a bit different on the package, but the same valve and controls.
These units I have found to last for about 3-5 years, some more but are made to be replaced over major replairs.
Fleck or Clack valve would be a better bet for long life and fewer problems down the road.
RO or distiller is going to be the only way to pull sodium out of the water, nothing else will work.
If you are on a well then a sediment filter is a good idea.. if you are going to do one, make it one of the ones called a Big Blue.. while any number of them might be white today, the filter that goes in them is 4X10 or 4X20 much better flow rate and less pressure drop.
If you can run 1" great, but if running 3/4 then try and use as few elbows as possible, use bend supports when ever possible for turns.
Some will say that the kitchen cold is to be untreated, others say treat the whole house... it is easier for whole house than taking off for the cold at the kitchen.
The above are just some of my ideas and thoughts on what you have brought to the forum.