I'd suggest you have BOTH the frizzen spring AND the cock (aka "hammer") spring lightened. Both are probably FAR too heavy. These heavy springs are what is causing your flints to need sharpening after only 10 to 15 shots.
As far as your frizzen goes... it should not need polishing nearly as often as every 100 shots... or even every 1,000 shots unless it is too soft or the heavy springs are causing the face of the frizzen to be all marked up, sliced and pitted which is a strong possibility.
Lightening those two springs will possibly cure all your rifle's ills... or maybe not. But take one step at a time... lighten the two springs, polish the face of the frizzen and wipe the frizzen pan clean of debris and crap... and go from there.
Good luck... and make
GOOD smoke...
Strength & Honor...
Ron T.