The time line given by your doctor, at least in my mind, shows how uninformed he is about mTBI. As klaus said, there is no way to predict recovery timelines.

The atlas chiro work may possibly be the cause of your regression. Especially if the chiro did the twist and pop treatment. This can be traumatic to the tissue surrounding the facets of atlas/occipital condyle. Inflammation in this area can cause decreased vertebral arterial blood flow.

btw, I prefer to use baling wire. It holds better than duck tape. LOL