For 1, he has infernal tattoos on his back. I think he's some sort of experiment Cazador has been playing with, and he received some devil assistance with it. Perhaps the reason the mind flayers took him was because his soul was put back, returned from Avernus where it went when he died, in his undead body prior to the abduction, and now the tadpole has twisted him into something even more unusual. Who knows?
Either way, I think the whole point of Astarion IS that he is not some soulless undead monster, but he has been somehow turned into a half living, half undead being - prior to the tadpole. Why else would Cazador treat him so unusually?
Or he's totally lying about everything and he actually is Cazador, playing with you and making you think he's got a soul. Lol
If Astarion is Cazador, I will shit myself in sheer astonishment and upload it to the forum.
(Please don't ban me; I'm only joking... or AM I?)
Remember the human (This is a forum for a video game):