​What is the purpose of salt in fermented vegetables?
Purposes of salt include


To draw liquids out of cells via osmosis (beating the vegetables up first also helps with this) which creates a brine. You want a liquid as the competitors to lactic acid bacteria like oxygen, so you minimize that by keeping the fermented material submerged in the brine the salt helped create.
Salt hardens pectin, which alters the texture of the vegetables (more crunch).
Lactic acid bacteria also like a slightly salty environment, and competitors do not.
Adding salt avoids putrefaction (preservative).
Adding salt limits booze-causing yeasts; if you do want alcohol production, that's a different discussion.


The salt percent can be as low as 0.8% but is more typically higher, perhaps 1.5%; too high a percentage of salt can inhibit lactic acid bacteria (a goldilocks problem). So in your case it may help to try lower percentages, perhaps 1% or 1.5%, depending on how accurate your measurements are.

High salt ferments (preserved lemons, etc) probably should be avoided.

A soak and rinse of the fermented materials may help reduce sodium, but could also wash away nutrients.

You could also try salt-free ferments, though these may or may not work out as the lactic acid bacteria will have more competitors and there will be more putrefaction (softer mushy texture).