I absolutely doubt that this diagnosis is firm. I would have those X-rays analysed by a third party assessor who would examine them in relation to the problems without a monetary expectation related to outcome.On one occasion when I had lower back spasms (unconnected to riding) I went to a Chiropractor and he said that the x-rays he took showed that my neck and spine were tilted a bit to one side (I think to the right). I guess not surprising for a 45 year old who sits at a desk (I am a lawyer) and often with poor posture.
On another note, boy I wish I could treat some people on this forum (interesting cases), particularly because I am a muscle and balance kind of therapist. Unless you have had significant trauma (or even if you haven't), much of your issues could be rectified by posture analysis, muscle length shortening analysis, or muscle patterning examination.
i do not disagree that you may have poor posture, however if you can correct your posture (look in a mirror) it is more than likely that you have muscle problems concomitantly. Bony remodelling, stiffness, and ultimately arthrofixation (stuck in one posture - as I like to call it) occurs over a long time and usually to damaged immobile joints, or in elderly in static postures. So your problems should be correctable with some good help[-