I agree with the others regarding the risk of atrophy. The only time a neck brace may be OK is when you sleep but learning good neck posture/discipline when sleeping would be better.

Of all of your symptoms, none really sounds like they could be from the neck. Maybe the low grade head pressure if you have spasming muscles at the top of your neck. Floaters are just a perception issue. You injured brain does not filter out the floaters where a healthy brain would see the same floaters and ignore them. Most floaters are just debris in the tears.

Most chiros are too aggressive and do not contribute to improving flexibility. A good physical therapist may be better.

You may benefit from an exam by a neuro-ophthalmologist.