imho, a very typical gun for the napoleonic time.
a 22 ga is a problem when it comes to wads. I made the maths: 454,4 gr / 22 = 20, 65 gr leadball = 15,2 mm diameter

maybe 20 ga wads will work if you can get them. for repairing the hammer I would give it to an experieced TIG welder, they do wonders.