Can you take the main cylinder pin back out of the gun?
If you can do this, then take the cylinder pin and cylinder out and try pointing the revolver UPWARD and then draw the hammer back. Watch the transfer bar and how it works. If you point the gun downward, the transfer bar will lock against the firing pin.
Now that you've seen this, put the cylinder back in and install the cylinder pin. Point the gun upward and draw the hammer back. Then try it pointing downward. If it works pointing upward but not downward, then the pin on the end of your cylinder pin has either been broken off or jammed into the socket. It is no longer pushing on the transfer bar back far enough and the transfer bar is not clearing the firing pin.
If what I've described seems to be your problem, then all you need to do is buy a new cylinder pin.
If this doesn't make any sense and isn't remotely close to the problems that you're having, then I don't know what to tell you. I think a gunsmith might be the next step. Sometimes it's hard to describe a problem in words without SHOWING someone what is wrong.