I would suggest a backwashed AN filter which would add 2-4 gpg of hardness to the 2 gpg and then a softener to remove the hardness and iron. The AN filter may remove some iron.
By nitrogen I think you mean nitrate or nitrite. If it is nitrite that is serious and it should be removed because the EPA MCL is 1 ppm and 10 ppm for nitrate with the combination of the two not to exceed 10 ppm. At least that is what it used to be.
He should have a Coliform bacteria test.