There are custom enchants that make you deal more and take less damage. You can do /enchants and see the ones.
The enchants that help you deal more damage to bosses are
1. Muscular
2. Rage
3. Fast Turn
4. Sharpness/Smite
5. You can get the enchantment "Drunk 2" on your armor which gives you permanent strength 2 along with slowness.
Armor wise I'm not really sure, but just get e-gapples and you should be fine.