Both my Mom and Dad live with me and Mom has dementia. She asks me the same things over and over. To make things worse I hear Dad in their telling her things to do or ask that he knows upsets me. Sometimes I just want to scream at them both and then I feel quilty.
That you are NOT here for his amusement??
He is obviously trying to "get a rise out of you".
A little behavior modification is in order for him. Try ignoring him or walking away when he acts like that. Do something you know irritates him. Don't make a contest out of it, but if you give him negative reinforcement he may get the hint and start showing a little more compassion.
NO need for the guilt. Your mom has dementia which cannot be changed easily, but your father on the other hand shouldn't be abusing the one doing all the work!!!
Do you know why they keep pushing your buttons? ... Because they installed them!
Instead of responding properly, you're reacting to everything they say and do to upset you. Example: since Dad is the instigator, cut down his privileges as good parents do with their impish or brattish children. He's probably bored, so find something for him to do instead of laying around like a lounge lizard. If Mom wants to spin and spin like a top, let her. Or find something for her to do to channel all those random bursts of energy.
As a last resort, make them an offer they can't refuse: either stop the nonsense or move out. People will disrespect you only when you allow it, so make sure whatever rules you set are enforced consistently and lead by example.
Keep us posted.
-- ED
For starter's I would recommend that you get a copy of Coach Boyles Playbook for Alzheimer's for Dad.
Why not join a support group for caregivers and BOTH Of you attend? The book I listed above should help before going to a caregiver support meeting, but your father will not agree to going to a meeting, then perhaps there is a friend HIS age that YOU can talk to and explain the situation and ask for their help.
It takes a great deal of skill to maneuver the land mines of Alheimer's and without the proper knowledge you are BOUND to step on quite a few land mines.
If you can get your mother to attend a DAYCARE center to help give all of you a break. Perhaps while she is at the center you can have a calm converations with your father. Here is another article on how to deal with Alzheimer's:
http://www.alzheimer.guelph.org/downloads/12%20pt%20Understanding%20the%20Dementia%20Experience.pdf
You have to copy the entire link above (not sure if it will be a 'hotlink or not) but it worth the read.
I care for my mother but don't expect her to care for me. That's just the way it is & I've come to accept that.
The best thing you can do for yourself is to let it go. No point in having your heart broken daily. You're sowing seed on stoney ground.