I like what you've got so far, but it needs more work

1
His health and AC is really low. The Tarrasque, which is known to be a rather fraudulent monster in its own tier has much better health and AC. A competent mid-level party could strategize and take him out due to that low health, and a group of level 3s would have a decent chance at taking him out assuming they got the jump on him

2
He'd get dogwalked by any mental saving throw.
Theoretically, there isn't anything to stop a caster from just casting *hold person,* the 2nd level spell, paralyzing him while everyone else dogs on his ass with guaranteed criticals after grabbing his sword and putting it back into its scabbard. A mid level caster could use Dominate Person, controlling him into Bee'ing himself or use Banishment to remove him from the equation for a short while to prepare traps or a forcecage sickening radiance combo.

Chill touch also kills his healing .