I am so sorry to hear of your misfortune and the suffering you have had to endure. I know of no lasting effect of anesthetics on pre-existing asthma. Makes me wonder if your shortness of breath with exertion is on the basis of a problem, other than asthma. Three possibilities come to mind: 1) that you sustained paralysis of one of your vocal cords or tracheal stenosis (narrowing), secondary to the (presumed) tracheal intubation during surgery, 2) that you may have had or may still be having clots to your lungs (pulmonary emboli) or, 3) that you have not just a weak diaphragm, after surgery, but a paralyzed diaphragm, a not infrequent complication of cardiac surgery but seldom a problem secondary to abdominal surgery and/or tracheal intubation. Your doctor is correct in asserting that paralysis of the hemi-diaphragm, post-operatively, may take a year or more for spontaneous recovery to occur.
Another, much less likely, explanation for your shortness of breath would be some type of heart failure.
You should ask your doctor if these 4 possibilities have been considered and carefully investigated. The specific PFT’s that gave “numbers .. mainly in the 60’s & 70’s” might provide a clue as to the cause of your breathlessness. Do not hesitate to ask your doctor questions or to request one or more second opinions.
Good luck