If you're hitting 1" high at 50, you should not be 10" high at 100. I suspect this has more to do with your eyesight than the gun. The "six o'clock" aiming method may help. You can find plenty of info on it if you google it.

I shoot FPBs, and sizing is the trick to loading them. Once sized, mine insert into the muzzle with fingers only and slide down the bore easily. Once I contact the charge (Pyrodex RS) I lean on it pretty good to fill the hollow base and compress the charge. Pyrodex likes to be compressed. I don't know if that applies to BH209, but others may.

Also, sounds like you need to move your rear sight to the right a bit.