Do you have any arm pain or hand symptoms?
Was it a whiplash type injury?
Does the chiro do any upper cervical adjusting (c1 c2) ( special training for that)?
Might be something to look into..
www.upcspine.com
MRI words of tiny, mild & small make me think soft tissue is the main reason for your pain.
Some times seeking out or adding a new DC or PT with more techniques /modalities can be beneficial. A new set of eyes so to speak...
Does DC use a variety of therapies? Like ultrasound, IF stim, low level laser, trigger point work, and posture work?
possibly the top rib can become raised and sort of stuck and need to be dropped down, called rib mobilization.