I put a peep for the rear sight, but would like a smaller front sight, preferably a fiber optic, but smaller then the factory dot. Or any other options that both gather light and are more precise past 100yds. Any thoughts?
Couple of thoughts... You can get a thinner fiber optic rod - most Archery shops will have a variety...
Two - One thing that I learned in the military shooting on various rifle teams was what is called a 6:00 hold. You place the point you want to impact on the top of the bead.

With the sight setup I use the illustration shown in "H"
One other thing that helps me immensely is that sight the rifle in with what is called a PBR...
https://en.wikipedia.org/wiki/Point-blank_rangeWith a muzzle loader I set a 3" PBR - through a given range if the rifle is aimed 'dead on' the bullet will never be higher or lower than 3 inches. In most cases with a ML this works out to be about 3" high @ 100 yards and dead zero around 150-160 yards depending the weight of the bullet and the muzzle velocity.
This ballistic sheet shows what I am indicating.

Hope some of this might help...