Death is to good for him and he won't suffer enough, imprisonment is okay... But slavery he be forced to shame himself in public. Especially if the public learned of he's evil deeds. So I hope it's slavery
I hope she's allowed to get her hands on sain and let her destroy him. Both physically and socially, by announcing it to everyone what sain has done. Maybe even warn women of he's evil eye skill
Sounds like it to me, after all her and the prince kept in contact with each other through letters. I think the king trying to have the prince marry the saintess for power