You ask three questions so I'll respond in 3 parts.

1. A) Dixie Gun Works Union City, TN $25.50/100

B) James River Armory, Millersville, MD $24.00/100

C) Track of the Wolf, Elk River, MN $11250/25

2. Goex FFG, 60 gr measured in volummetric measure

3. "Musket caps" are what you want.

Get some "Bore Butter", a bullet lubricant available in stores that deal with black powder arms, use a palette knife to place some in the hollow base of the minie ball, then seat the minie ball, and fire. Do not use substitute powders like Pyrodex or 777. They will cause you a lot of grief. Do not clean with amonia, hydrogen peroxide, sources of much grief.

Good luck.