The forward protrusion of the firing pin is limited by the firing pin bushing.Something could have gotten between the front of the firing pin and the rear face of the bushing. I had one on a model 51 that acted like you described. Part of the rear section of the firing pin had broken off. You...
Try a new coil mainspring before changing the firing pin. The firing pin is J frame rimfire specific. I bought some on Ebay several months ago. Older rimfire firing pins are hard to find now. Jack First has some for K frames.
S&W single action trigger kit for K frame center fire, NOS in blister pack. Includes 1 trigger, 1 hammer and 1 single action spring. $100.00 shipped conus
I own15 J frame rimfires and 25 K frame rimfires. I shoot them regularly. The J frames will shoot just as well as the K frames. All but 3 of the revolvers were made before 1980. My wifes 317 has a good double action trigger and shoots well. Practice! practice! practice!
Get your eyes fixed. I had mine done and have 20/15 vision. I recommend Woolfson Eye institute in Atlanta. I am 70 and shoot vintage revolvers almost every day.
I have shot thousands of rounds of their .22 mag jhp in S+W revolvers. I cannot remember a single squib or failure to fire. It is also accurate. I don't like their .22lr.