@deme17z are the medications helping at all? Is the physio helping at all? Sometimes it’s time to call an end to ineffective therapies.
Are you able to have a schedule? Maybe if you regularly told him it’s time to go for a walk, it would help you both.
Are you able to get someone to stay with him while you go out?
Your frustration is absolutely justified.
You know, once upon a time, if a person was age 86, wanted to sleep, and was barely able to walk, family would let him sleep. Put him in a wheelchair. Not try to rehabilitate him/her.
My brother and I used to say “Dad’s 84. Let him eat what he wants.” (After 20 years of trying to stop him furthering his decline into eating unhealthy foods all the time.)
In the end, it was the incoming cancer treatment that killed Jim. He wanted to continue with it. We saw the side effects but it was his choice.
Sometimes we should just let old people do what they’re comfortable with because all the treatments and therapies are making their life more miserable.
Remember to take care of yourself!