Im getting about 1-1/2 to 2>>>>>>>>>>>>>
Thats about all you can expect with a standard of the shelf AR, that really good grouping.
Maybe also look into a different barrel with more lands and grooves and maybe some custom ammo.It might not be your trigger at all with those groups at 100 yards. I would be interested in seeing what transpires when you get the new trigger group.
Your groups are fine. The reason for the heavy trigger pull? Neanderthal Jarheads, and Dogfaces need to learn the art of the trigger squeeze...a heavy trigger is the only way to learn.
My trigger is the same, and it was the same with my M-16. Never change something that works.
Heavier bullets require a "faster" twist rate to stabilize the bullet. A 1:9 twist is pretty standard for bullets up to 69gr.