@merpreb There's one more thing that I would add to your list of things that affect breathing....Thoracic Outlet Syndrome... because for me it causes tightness in the chest and can prevent the muscles from fully expanding the rib cage properly. It involves the scalene muscles which are accessory muscles for breathing and emergency breathing in the neck. I have had muscle spasms that cause ribs to twist slightly. TOS can be caused by poor posture or an injury like a whiplash. It's like living in a straight jacket and can even cause a functional scoliosis of the spine. I did have that, but physical therapy helped straighten it out and later MRIs don't mention it anymore. Physical therapy with myofascial release often helps TOS and get the body moving better. I've been doing MFR for a few years.
Here are some links that reference breathing issues with Thoracic Outlet Syndrome and MFR treatment.
https://trainingandrehabilitation.com/how-truly-treat-thoracic-outlet-syndrome/
https://www.painscience.com/articles/respiration-connection.php
http://www.med.umich.edu/1libr/CVC/997ThoracicOutletSyndrome.pdf
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/