A commonly used combination is 17gr FFFG with that .375 ball. Some go with a .380 for a tighter fit, shaving a nice ring of lead off the ball as you ram it home. Some use a .36cal Ox-Yoke lubricating felt pad between the powder and the ball. Others dab a bit of their favorite lube over the ball in each cylinder chamber after loading.
My preference is 17gr APP in FFFG, .380 ball, no need to lubricate as it makes its own lube of sorts. Clean up is a breeze.
Have fun experimenting. I would agree with you, it deserves to be shot as it's not an original 1851.
RCJ