dnd 5e – Are the Divine option of the Sacred Weapons Channel stacked with the Dueling, Divine Smite and Oath of Devotion fighting style of the Sacred Weapons Channel?

I was in a DM game the other day when the Paladin from level 3 of the party gave a blow to the KO & # 39; d of a junior boss.

This is how he did it:
Total damage = two-handed longsword (1d10) + Str modifier (+2) + dueling combat style (+2) + divine hit (2d8) + sacred Weapon option of the Pledge Oath (+5 of Charisma) .

Using RAW, is this legal?

I allowed it to happen in our game because it was a great time to tell stories, but I just wanted to make sure that the rules were not followed. I read the rules after the fact and could not find anything that could prevent this from happening. Am I missing something?

Note: Yes, the PC is only level 3 and already has a Charisma +5 modifier. He was just very lucky to display his statistics.