Men get restless quicker then women. Your husband has a good attitude thinking he is still young.
But he needs to remember pneumonia is a serious disease, and can leave scar tissue on the lungs.
Maybe he can drive you to the market,you go in the market, and have him stay in the car. Better safe then sorry.
My late husband had multiple cases of pneumonia,so I understand your concern for his wellbeing.
Take care