Isn't there another one that decreases stability for ranged? I feel that one would be better on a Shotgun.
There is - Reinforced Barrel, more stability, less range. Also of note, Rifled Barrel - increased range, slower reload; and less desirable, Smallbore - increased range and stability, with slower reload and reduced mag size.
The only other possibilities for range increases would be tier 2, either Rangefinder or Shot Package - as already stated by the_co_founder, Shot Package. Shot Package, Shot Package, Shot Package. Unfortunately doesn't seem possible to get both.
For the last perk, Kneepads isn't great - my choice of three here would be Rodeo, Luck in the Chamber or Final Round.