I'm a terrible best friend.
What makes you believe that you are a terrible best friend?
It's because I had my arm broken for 4 weeks but I kept making him help me exercise at the gym.
It is good that your friend wanted to help you but it is not good to take advantage of their help and make their life more difficult. It would lead to them not wanting to help you again.
What do you want the poor boy to do?
Why not repaying your friend for all the help he gave you? I'm sure he'd feel like you'd appreciate all his hard work if you did something special for him. Your overall friendship would improve too.