So it turns out, after EMG/NCV of arms and neck that showed multilevel, bilateral severe radiculopathy, and MRI c-spine that showed similar severe foraminal and spinal stenosis, that this is the cause of most of my symptoms. The muscle weakness and tingling follows all the corresponding myotomes for each stenotic level. It's likely I have chronic costochondritis, and I'm pretty much deconditioned after 2+ years of being afraid to engage my core and use my arms. Seeing a surgeon on Monday.