Only thing that contradicts the theory that you can die to remove the tadpole, despite the game clearly showing that this is the case in a scene, is that when Wyll dies he never has a tadpole leave his body.
For me he died 2/3 playthroughs at the gates of the druid grove. And both those times no tadpole no matter how long he has been dead.

No idea if its oversight, unfinished cause beta, plothole, weird tadpole stuff.

And then theres yeah if Astarion kills during feeding... why did the tadpole not leave a corpse?

Might be plot, might be not. I'm kinda iffy about if they make it a special tadpole that is special amongst special tadpoles. A bit too much special for me.