This interpretation is on my mind because I recently watched the truly terrible Sci Fi adaptation of the Wizard of Earthsea (don't! it's sooo bad! but do read the books if you haven't) and have been realizing how many parallels there are between Ged, Wizard of Earthsea and Gale, Wizard of Waterdeep.
Like Ged, Gale was progidy, a golden child. When Ged went to university he learned the secret names at an astonishingly fast rate, his memory was far superior to other students. And, of course, this earned him the enmity of his peers. And yet Ged felt inferior to them because he came from a poor village and because he had been trained by a
woman. (Earthsea being a patriarchal culture where women's magic was thought to be wicked and weak) Goaded on by a playground duel Ged sought to prove his superiority to the other students. Like Gale, Ged found a book of forbidden secrets that contained a spell that he was warned was far above his ability to cast. But Ged was the star student, the valedictorian, perhaps even the chosen one -
no spell was above his abilities! Suffused with Hubris he cast the spell, and successfully summoned a dead spirit. Only to be attacked by a shadow. His shadow. A being that nearly killed him and that destroyed much of his magical acumen. The shadow stole many of Ged's skills, he learned at a far slower rate and had to quietly depart the college as a C student, not the valedictorian.
He is hounded by his shadow for years and he tries to face it, unsuccessfully, a number to times. Until he finally realizes that he can no longer run from it. He will come to terms with it even if doing so kills him.
For me the bomb moment parallels the moment when Ged turns to face his shadow. He looks his failures in the face and no longer seeks to blame his misfortunes on his ex. With both characters it's hard to say where the feelings of inferiority end and feelings of superiority begin, they are twin traits that eat each other's tails and feed on the other. BUT for all the good things about the Gale romance he still pins his failures on Mystra and not himself. Don't ask him about Mystra! You won't like the answer. In the romance has wrestled with his shadow but not yet defeated it.
Gale only defeats his shadow when he offers to detonate. He has learned to care something other than his personal ambition. This, IMO, is best ending of romance because there is
no greater love. His act not only saves his friends but destroys the object that could have made him a god. Love achieved, Hubris destroyed. Success.
