I feel the exactly same way ! Excellent points there and I have the similar questions - It felt like none of my choices / consequences mattered.
the I just finished the game last night and I have to say I was disappointed. Act 3 felt rushed and is (for me at least , buggy as hell). Which is a shame because Act 1,2 and early Act 3 were Fantastic !!! the best gaming experience I've ever had !
I romanced Astarion - Good outcome. And the romance ending honestly feels like an afterthought. Like they spent so much time and effort on the evil ending (which rules) and then just hastily threw this one together. There's nothing remarkable in there. Not a single noteworthy line, just empty bla bla. And I know they want to emphasize user choices but to me it feels so unnatural that even after all this, astarion STILL asks if you want to stay with him. After declaring your love for each other, What kind of monster would leave him at that point? That's just not how relationships work. You don't ask every single day "hey do you still want to do this?". You both commit and then that's it. Ugh.
As far as I've seen, astarion is the only companion who has to suffer like that (him burring in the sun) after choosing the redemption path and it seems so unfair to me. Like why can't he be rewarded for making an effort to become a better person?
Your Love interest means nothing in the end, not even a hug or kiss. Like we have been able to do since growing the romance.
The Necromancy Book of Thay was Pointless & Useless !! I thought it would give an advantage against Cazador or even help cure Astarion.
Allies for your final battle don't even show up, like the Nightsong or Mizora. Even though they say they will be there in the end to aid you.
I would have liked to see something of what I've achieved after my 80 hours gameplay. Slideshows, animations , just something to show how my choices affected the world.