Dear FortunateOne,
You really have a lot going on and have done a wonderful job of writing it all down to look at as a big picture. I hope you have shared that list with your doctor to consider. With so much going on in so many parts of your body it sounds like there are some nerve stimulation messages that are not getting through.
What does your instinct tell you it is? Do you believe the problem is related to your cervical spine? thoracic spine? lumbar spine? internal organs? lack of activity? too much activity?
I hope you have some relief soon and are able to envisage getting your body back to the level of April 2014.
I have a lot of nerve issues and spine issues due to Hypermobility Ehlers Danlos Syndrome. So I am able to relate to the issues of pain, numbness, weakness and not being able to sit (or stand or walk or lay down) for long. I have skin issues and allergy issues but I have nothing like the cysts you describe.
It is interesting that your cysts are on only one side of your body. Maybe research symptoms of connective tissue disorders, mast cell disorders and CRPS. Maybe something you read there will point you in a direction to research further in your quest for answers and journey back to comfort.