How to get a crabby Dad to move arms, legs (safely) while in chair? He was in hospital 3 weeks. Little rehab and I want to prevent decline.

Can you hire a PT person to come in to work with your father? He might co-operate more during a designated session with a professional than he will with family prompting.

I would guess that with the hospital stay, your dad is extremely depressed. With the hospitalization, dad must be overwhelmed with thoughts about his life ending and, like my dad (91+), may simply want it all to end which is scary. To get him to exercise in his chair, I tell him that I feel out of shape and I ask him to HELP ME by doing some chair exercises or IF you think you can, would you go for a little walk with me? I don't know if it's right to some of you but my dad feels USELESS since my mom left us. He comes to life when he thinks I need him. Older people are so often swept aside and feel they are a burden. Making him realize I NEED him... he gets cranky and abusive at times but when he believes he is NEEDED, he is a different person. When people lose their will to live because of depression and fear, pull them back because they are USEFUL & NEEDED. Sometimes I get flustered and try to be forceful in getting him to exercise, but peace full, love full with a pinch of determination and neediness really helps. God bless you.
"You catch more flies with honey than with vinegar".

He is 93. If you can make his therapy more interesting with games etc., fine. But if you can't... you may just have to accept that he has the right, as all of us do, to refuse a therapy he doesn't want.
Maybe he's just tired. I think many of those who live to his age are!

This can be a time for generations to re-connect, to share mutual memories, to reinforce the bonds that have made life meaningful. He may not last much longer. Therapy or not, it will not help anyone if these last few years or months are marked by stress and conflict.