Scar tissue brachial plexus debulked surgically 2010; residual weakness, inflexibility hand, wrist; pain there now with heavy lifting. Avoid lifting?

Get re-evaluated. Find a vascular surgeon with experience in area of brachial plexus problems or thoracic outlet syndrome, as these issues are complex and often solutions can be devised. In most cases, specialized EMG studies will be needed to ascertain what is occurring, and this too will require finding an experienced clinician.
See doctor. Not sure what is going on, but i tell my patients that if something doesn't feel good, refrain from doing it. You might consider seeing your neurosurgeon if things seem like they are worsening.