Sigh.
He makes mistakes when he's not in control of a situation. It's - not usually useful for him to make mistakes, usually they make things worse, it's good to know how to do that if you're positioned to take advantage of the mistakes but otherwise it's better to leave him in control of things. He likes being obeyed. He likes being trusted, including in very narrow and restricted capacities. He'd like it if you cared about him in any sense but faking it is worse than nothing and I wouldn't blame you for not wanting to self-modify in that direction.
I got there mostly by concluding that it's - so sharp a disconnect from what he is in other capacities, and we were all doing dangerous mind-altering stuff in Valinor in self-defense, that I think he broke something. And someday we'll find the way to reverse it all and he'll be so horrified. I don't know if that's true. But caring for the person who he really ought to be is close enough to work.
He's easily convinced to do something that's actually better for the country than what he's currently doing, with the honestly bizarre exception of 'stop keeping captive boyfriends'. Moral arguments are better made as personal sensibility ones - you hate mindreading and he'll accommodate, you think mindreading is morally objectionable and he'll ignore you. That one's related to all the Vala editing for ethicalness, back in the day.
I have sex with him. That one depends - almost entirely on how you're going to feel about it, strategic unhappy obedience makes him happy and contempt makes him angry. If I'm in an acceptable mood it works really well, though. He will sometimes respect a no but not reliably. Pragmatic arguments work better than moral ones, again - 'that would make it a lot harder for me to feel comfortable around you' works better than 'has anyone explained that rape is bad'.
When he makes mistakes he'll regret them and usually be agreeable about concessions to make up for them, not that the concessions will be sized to match the mistakes.