I am 63 and had a knee replaced last August. Your numbers are a bit better than mine but I also struggle with asthma/low lung capacity. My VO2max has always been in the bottom quartile.
Low intensity coming back is the name of the game. I do not have a sprint but can do 140-150 watts for hours. Took 4 weeks post-surgery to be able to get over the top on the pedals. 6 weeks and I could spin about for 30-40 minutes. In May I did 50 miles/day in a bike tour.
PT will hurt but the more you do, the quicker/better the recovery. Good Luck!