Like, this is how deals with devils work.
First deal "Ill do everything I can to remove your tadpole", when he knows he can't remove it but technically, he honours the deal. Second deal, i'll give you the hammer (which I have no use for and am 90% you cant use but if you can it'd get him the crown) and gives you a way to liberate Orpheus which if you've done L's storyline you really want to, but at a greater cost, ITS A DEAL WITH A DEVIL, why would you expect to get a fair shake out of it?
we wants the crown, and he wants you to give it,
As for telling you where it is, he's the ruler of a hell,he was tempting you by dangling it within reach, not expecting you to pull off the heist thats a classic bad guy thing
I don't think you should get a fair deal, but I do think he should be better at manipulation. The earlier he offers his deal, the
less likely you are to have caught onto the tadpole not intending to harm you
