What happens when you go to the stock main spring. In my opinion smooth is way way more important the light. You could also go to the hardware store and get a socket headed 6-32 screw a 1/4" or so longer than your stock mainspring tension screw and use it. Keep tightening it up until you get 100% ignition. Then when you know how much you need sticking through the frame against the spring, shorten it so it is tight to the frame with that much stick in.

Are there any rub marks on the side of the hammer or firing pin that indicated it is rubbing somewhere? Probably just not enough spring tension to reliably fire. You don't need to make trips to the range, just use a bunch of primed cases to test for ignition. I would much rather have more than enough, than be border line. If your piercing primers with the pointy pin go back to stock one. What kind of primers.