The fact that he's taking so long to right himself is a key sign of a neurological issue. A healthy boa will fight being put on his back in the first place and will immediately twist upright. I am thinking that is what caused the regurge and not the other way around. Regurgitating is often the first sign of a neurological problem. Could he have possibly overheated?? He can move his neck just fine - in the first scene of your vid, you can see the s-coil from his head down his body when you moved him. And later his neck is kinked from the opposite side. It is "kinked" because he's not right in the head, not because of a physical injury. I am sorry, but that's what I see. The good news is that if he developed some neurologial issues due to overheating, and because he's so young, some of these symptoms may go away with time and care. Only a qualified herp vet can tell you for sure.
I would immediately quarantine if you haven't already. Lower his temps a bit - like an 86ish hotspot for now with 78ish ambient. Get him to a vet asap. Don't try to feed again until he's seen a vet. And keep us posted please. Wishing you luck.......