Great conversation.

Two things come to mind:

1. whether I can restrain my stream of consciousness or not seems irrelevant to whether I am free to act/think, because it simply addresses a similar but distinct issue: how does our subconscious impact the "self" and self will.
2. whether brain scans can predict behaviour reliably or not, seems unproven still. The examples you cite need to be closely explored before I could conceed that point. Why? It seems the metrics of observation are necessarily, intrinsically, inadequate.
   You suggest that because we can see indications of choice before actions unfold, even before the actor realizes they have chosen, means the choice is not our own but what if the thing that chooses is metaphysical? What if beyond the physiology that is measured we have a soul that decides?

Of course I cant prove this but it is not disproveable either.

Seems to me the question that comes first is this: not are we free but what are "we", not whether we have free will but what is the "self" at its core. Mind or matter? Physical or metaphysical?

Love to hear your thoughts on my response.

P.s. your post is like some Black Mirror or Altered Carbon $hit. Great stuff!