I believe most of what goes on is unconscious, so to claim you know yourself completely is like knowing the future. You can make predictions and be good at it but only the future can tell you what it holds. Only after death can your entire story be told.

The mind is an emergent property of brain stuff. It's like a game that emerges from a rule set. Can the game break the rules? Even when one of the rules is to follow the causal chain? I don't think the chain can be broken. It's my assumption.

I think the only reason anyone would assume the chain can be broken is a feeling. The feeling of agency, the feeling of self. Things that we absolutely unconsciously construct in our minds to be able to make decisions. It's decision making machinery.

Imo. I'll always assume that the causal chain cannot be broken. I guess until I don't

Uh I guess I have no idea

"the development of events beyond a person's control, regarded as determined by a supernatural power."

Going by Google I'd have to agree with you. However, supernatural power is by definition unfalsifiable. We have no idea and we can never know.

It doesn't really matter though, as long as you don't claim to know the future.

Edit: "atoms may deviate from their expected course, thus permitting humans to possess free will" this is a logical leap into the supernatural. The idea that we somehow have the ability to influence matter from outside it's causal structure.