Wow... that was... a rather impressive post.
I agree. I'm impressed by the quality of the writing and the strength of the authors convictions. I also strongly disagree with the premise. I don't think Gale was victimized by Mystra and find the comparison of Gale's treatment to that of child abuse . . . supercilious? It's overly strong analogue to apply to a silly story. Child abuse is a very serious issue and shouldn't be invoked in such a manner.
If Gale blows himself up he is all but assured a place in the afterlife with Mystra. Someone who is always asking to be directed to a good library is ends up spending eternity in the best library in existence. When Gale was a chosen he was granted god level health (passive regeneration, immunity to aging and most diseases), immunity to a host of spells, the ability to free cast some spells and the ability to use silverfire. As long as you don't die in a vat of acid you are immortal - no need for mephits or underemployed death gods. Gale was also free to form any sort of romantic relationship he wanted with mortals or other gods. Being chosen is not nice thing and is not abusive. My Tav would take the offer in an instant.
What Gale did was not evil but he created quite a mess. Mystra is both the internet and the sysadmin of the internet. Gale was someone who downloaded a virus that destroyed his laptop and and is now spreading to other computers. Were Mystra vindictive she could launch Gale into the shadowfell and let his orb detonate there. Instead she lets the virus spread across the internet in the hopes that Gale would use this crisis as an opportunity to show he is worthy of his status as a chosen. If Mystra is to be faulted for anything it's putting her personal feelings before her duties as sysadmin. How many servers did that virus take down before Gale fixed his mistake? How much of the weave fell victim to Gale's Folly?
Granted I've not romanced Gale so I only know him as a companion and my cleric of Mystra made it clear she didn't want hear him talk about her god as if she were a crazy ex so I don't have all the dialogues others do but I think Mystra treated Gale rather well. And of course she forgives him every time he fails to enact her plan . . .