If you use Shield Breaker on a neutral monster, the damage you do is going to still increase.
There are no monsters with "worse" gun resist. If the monster is healed whenever you use attacks, it's the gun resist. Using Shield breaker removes the gun resist property to let you deal damage.
Chimu's banish is small because it's not a boss. It's just a spawn to annoy players with a smaller banish.
The actual bosses unique is the same size as Bolster Ballad [mastered] if you ever saw a sheep with one.
Sadly I have no pictures of it.