Hi and welcome to the Chiari forum.
I am sorry to hear your symptoms did not resolve with surgery, but for me , and I did not have a syrinx it took a few years to see all the benefits I recieved from my surgery.....and you have to look at your surgery from August....you are only 2 1/2 months post op.
Neurological pain is difficult to treat even with meds.....so sometimes what we do or how we do tasks can help. Only tou know what activities trigger your symptoms to worsen....find new ways to do the task to see if it helps...take more breaks during your day to lessen the impact of the triggers.
I knnow you said this did not show until you were 50, but I truely believe that since this is a congenital condition that those living with this accept how we feel to be is "normal" when in fact we are dealing with symptoms but not aware what we are feeling is a symptom since we have always felt it and were able to deal with it, it is not UNTIL the symptoms worsen for what ever reason that we take notice.
May I ask if the surgery on your arm was for tarsel tunnel?The longer that a syrinx goes untreated the longer it is causing nerve damage....so, it can take even longer to see results after a surgery, it is not instant.
Have some patience, change some of your posture and movements, and take rests periods.....and most of all LISTEN TO YOUR BODY it will tell you when to rest.