Of course, if you look at Gale and Mystra's story not as a couple's relationship but as a "goddess and a misbehaving mortal" story, there would be a different perspective, but isn't that demeaning to Gale himself?
I think, that is a very black and white way to look at it, either become a god or grovel before Mystra. The whole God of Ambtion thing seems to be something he does to spite Mystra and to show that he can control the Crown. The whole mess started because he wanted greater knowledge and understanding of the Weave, becoming the God of Ambition gives him none of that. On the other hand, following Lae'zel's advice to trust in his own immense talents and the mighty company he keeps, would. When you talk to him about Shadow Magic at the beginning of Act2, he seems tempted to try if he can handle it. He also seems to have no objections against using it because for him magic is just a tool and what you use it for makes the difference. The only reason he does not use it, is because Mystra forbids it. So the best solution seem to be, to just care less about was Mystra says and instead to rely on his own moral compass and the opinion of his close friends.
That leaves the Crown - and it's probably for the best if Mystra keeps it safe, otherwise it's just a matter of time before someone causes havoc with it again - most likely Raphael. So just give it to her and be done with it and with her. I don't see anything wrong with that. At the same time the Graveyard Scene doesn't leave me with a mournful feeling, quite the opposite. Starting something new is always scary.
Unfortunately, this is a fail for Gale's story. The bomb in his chest was supposed to be Gale's curse for encroaching on Mystra's place. His original storyline was similar to Astarion's in that he always wanted to be a God. Then that got cut out, with the description on the website being changed right for the game's release.
All of the stories could have been more in-depth, but each one was softened. Now he's just a "good mage who wanted to please the goddess". But he was supposed to be the prototype for the new Karsus.
