I think the message of Howl’s Moving Castle is that in order to maintain a successful relationship with some kind of fucked up wizard, you must find it in yourself to also be some kind of fucked up wizard.
See, I don’t think that’s the case. Certainly, Sophie’s magic is often more practical than Howl’s, but if you think that the practicality of one’s magic is a reasonable measure of how good a fucked up wizard is at being a fucked up wizard, you don’t understand fucked up wizards.