Powder by volume
1.) Start with 20 grains by volume and go up until you lose accuracy. You will find what the pistol likes.
2.) I agree with Hawg in that lube is not necessary if you use wads.
3.) I hate to say this because it will open a can of worms but, I don't think it's impossible for a chain fire to happen from the nipple end. In fact, I think it's much more probable to happen from a poorly fitting cap. (I could be out to lunch here but would rather err on the side of caution). Far too many guys use caps that don't fit properly, "pinch them" etc. and that being said, I've never had a chain fire. (Knock on wood).
4.) This is not necessary, but when I get a new pistol and before I even fire it, I replace the nipples with AMPCO/Treso nipples that use a #11 cap. This way, everything I own uses the same caps. They fit TIGHT on the nipple and I have no problems.
5.) This being said, 1.) I don't have to monkey around and remember what pistol uses what size cap. 2.) I LOVE shooting my BP firearms. When I do have the opportunity, I grab my stuff and go. Everything is the same.
6.) I am doing it properly to the best of my ability and knowledge including safety.
7.) I love this (sport?) and could care less what it costs me to have fun doing something I love doing.
This is the best advice I can muster. Everyone here is neither right or wrong but you will hear their opinion!
All the best to you gentleman,
Birch