That's fair regarding your Halsin point. As for the gods though, I think that's far more problematic. Firstly, there have been fans in this forum who've poited out how Mystra asking Gale what she does is out of character already, and more in line with Larian's interpretation of gods in their other games. But beyond hat, maybe its because I'm a person of some faith but I don't think Mystra's request is that outrageous in this context. She's not just a person acting out against an ex because she's mad. She's a goddess with higher understanding, responsibility and knowledge, asking something of a worshipper. Specifically She's asking for a redemptive sacrifice that's also meant to serve he greater good. Gale sinned against her as a goddess and now she's giving him a way to atone. Presumably once he dies, she's claim his soul for whatever afterlife awaits her worshippers and all will be well in that respect. The stuff with everybody turning is bad, but I look at how if Gale explodes in act 3 everything is fine for no reason and just chalk it up to bad writing.
So while I agree Mystra's request is harsh and morally gray, I think that's leaps and bounds different from having one perfectly innocent man murder one of her worshippers just because you don't want her dating your daughter. That is leaps and bounds more petty and like you said, it ruins Shadowheart's story and at that point Shar kind of seems like the right choice to side with and Selune loses all appeal. Maybe if for some reason he relationship was putting he greater good at risk somehow, like threatening to put Aylin in Shar's power and thus make Shar stronger, then it would work. But that still feels iffy frankly.
