Have you tried different pellets? Heavier pellets would reduce muzzle velocity and increase retained energy. The accuracy is said to increase markedly once the muzzle velocity drops below the speed of sound (about 1100 fps, depends on temp and air pressure).
I regularly harvested squirrels with one shot with the old Beeman’s Silver Jets and the trusty Sheridan.
I bought a range of pellets to try out which ones work the best. I have some with red plastic tips, some called ‘perpetrators, some called ‘devastators’ etc. And you’re right, the heavier ones slow down a bit but are still faster than some .22 rounds.