I am not a gunsmith by any means of the imagination. Do whatever I suggest at your own risk...that said and out of the way..I wouldn't remove the frame pin. Instead, first review how to disassemble the slide...in particular how to remove the firing pin. There is a cover on the back of the slide that must be removed. I would try pushing the slide back as far as I could; hopefully there is enough clearance for the back plate to slide off. If there is space, and it won't release, have someone pull the trigger while you try to slide it off.
if it comes off, then pressing down on the metal at the bottom back end of the slide while pressing the trigger should release the firing pin. Hopefully, you can then remove the slide.

Check the snap cap to see if it is still good or if it was "capturing" the striker.

Good luck,
PaJ