Thank you so much for this post! You've opened my eyes to a lot of things, perhaps if I had read something like this earlier, the game would have cost me a lot less nerve cell
I felt genuinely sorry for the other spawns, especially Sebastian (and Astarion, judging by his facial expression near the cages, didn't want them dead), and I didn't really consider any options at the time other than freeing them all. But you're right, many of them will start killing innocent citizens of the city, and their very lives will also be full of suffering, and that's an additional argument in favor of the fact that there's no point in discouraging Astarion from the Ascension.
The dialog you mentioned really discouraged me the first time too (thanks for mentioning the mod, I'll look for it). I had to choose option b and say the other, "my" line out loud. It wasn't until much later that I realized that Astarion wasn't offending "me", that he was essentially interacting with a completely different, externally imposed character. He can't "offend", he doesn't know anything about any "offenses", it's just that the writers have some ideas of their own, not only about Astarion's behavior after the Ascension, but also about Tav's character and the nature of the relationship between the characters.
The interference of other authors in the script, perhaps, makes the arguments about "What did the Larians want to say?" somewhat meaningless. Perhaps the whole "moral" lies in the fact that when a true creator leaves his creation behind, in the hands of others it begins to wither.
The fact that Astarion is a bit "possessive" is something I even like. It's nice that he doesn't want to let Tav go far away from him. And the fact that Tav is becoming his spawn is clearly comforting to him (given all his mistrust). It's much better, much more fitting to me than that scene of the final conversation between the Unascended Astarion and Tav, in which he actually suggests that Tav abandon him.
And yes, his animations are adorable. And I'm now taking him to every mirror on the way to enjoy the line
