Yes, Vintage Gun Grips makes replacement butt plates. They offer several for the Flues model. Best to trace the end of the stock and mark the holes to get the right one. (Ask me how I know.)

As far as ammo, I would recommend low pressure 2-1/2" loads from RST or Polywad.

While the two different barrel manufacturers is unique, I don't think that is what it made a special but I am certainly no expert. I'm sure others with more knowledge will chime in.