How to enable mom to sleep despite dad constantly waking?

I'm worried about my mom because her sleep is being ruined by my dad. I'm particularly worried because she is genetically at risk for Alzheimer's.

My dad hasProgressive supranuclear palsy (PSP). He can barely walk on his own. He needs help getting in and out of chairs and beds and cars, and he needs help with peeing. His doctor recommended and supplied condom catheters so that he doesn't need to get up at night to pee. However, my dad doesn't use them. I don't know why, and he doesn't give a straight answer as to why. So my mom gets up 2+ times a night to help him pee into a urinal.

As if that's not bad enough, my dad has recently been waking up in the middle of the night to just get out of bed, to maybe start his day, to maybe just sit in a chair - who knows. He goes downstairs himself, turning on all the lights. He comes back upstairs, leaving all the lights on, complaining that it's cold, and that he wants to sleep again. This is all despite the fact that normally he can barely walk on his own, so it's dangerous for him to be going up and down stairs. My mom doesn't realize that this is happening - she only realizes it when my dad inevitably wakes her up so that she can help him back into bed.

What can my mom do in this situation? How do I help both my dad and her? Something to consider is that he doesn't realize (and becomes indignant when we gently explain to him) that he is causing so much trouble to my mom. My mom is at a loss for what to do.

Any help would be greatly appreciated.