The Hit/DC in his spell tab refers to the spell's required saving throw to resist that spell, not the spell save DC the target must make.
That means the spells Command, Compelled Duel, and Wrathful Smite all require the targets to make a Wisdom saving throw, and if they hit a 13 against your spell save DC of 13, they succeed.
What you're referring to about Charisma is how his spell save DC is computed from. A paladin uses Charisma as their spellcasting ability. It's computed as 8 + spellcasting ability mod + proficiency bonus. So his spell save DC is 8+3+2 or 13.
Here is his sheet https://www.dndbeyond.com/characters/80766392
Not sure why his spells are utilizing wisdom rather than charisma?
The Hit/DC in his spell tab refers to the spell's required saving throw to resist that spell, not the spell save DC the target must make.
That means the spells Command, Compelled Duel, and Wrathful Smite all require the targets to make a Wisdom saving throw, and if they hit a 13 against your spell save DC of 13, they succeed.
What you're referring to about Charisma is how his spell save DC is computed from. A paladin uses Charisma as their spellcasting ability. It's computed as 8 + spellcasting ability mod + proficiency bonus. So his spell save DC is 8+3+2 or 13.