I googled this rifle up, not much info available.
I did learn that it has a 1:48 twist.
This is an intermediate twist, which gives good accuracy with patched round balls, as well as with elongated slugs.
Why don't you use what the pioneers used, the patched round ball. Get a box of .490 round balls, and some pillow ticking. Get some Old Zip patch lube from dixieguns.com and you are ready to go.
Try 70 grains of black powder, then try 80 grains, then try 90, see what your most accurate load is.
With 70 grains of powder you can kill deer and hogs all day long with this rifle. The patched round ball is a proven game getter, is traditional, and is the cheapest way to shoot.
From looking at your rifle yes, I assume you would use number 11 caps, they work great and are, likewise, cheap.
You also could try an elongated slug, such as the Buffalo Bullet etc., they are fine but more expensive.
They don't like to talk about sabots on this forum, if you want info on sabots you must go to the inline forum.
Really you can probably do everything you want to do with the good old patched round ball.