Tr6driver,
I had to do some work on an 1849 pocket revolver, and found the following link to be extremely helpful. I think, in the end, you will find that you might end up filing the top of the bolt.
http://www.theopenrange.net/articles/
Refer to the "tuning the Pietta" part 1 and 2.
As for the load, don't worry too much. If you can fit powder and ball into the chamber, you won't be over-doing it.
Colt Blackpowder (no relation to the Real Colt) recommends 12-20gr for their Colt Signature Series 1862 Pocket Police, with 15 gr being the suggested load.
Short is, find the load your gun likes the best. It' likely not to be the largest powder charge the gun will hold. I'd start at 15gr 3F and go up and down from there.
Consider a filler such as corn meal to bring the ball close to the mouth of the chamber. Corn meal is compressible, so you don't have to be precise with it.
That's a pretty gun, wish I had one...
Cheers,