Got a spray bottle? One or two squirts with the the bottle to the CAT when he beats up the dog should probably teach the cat his antics are NOT allowed, nor will they be tolerated. If you see the cat approaching the dog, give the cat the "AHH AHH!!!!" sound....it'll probably wake up the dog, but it'll also probably stop the attack!
Contrary to belief, cats can be trained...ALOT harder than dogs in some respects, but they can be trainedl...
If the dog gives chase, correct the dog - again, NOT allowed. Granted, the dog probably wants to beat up the cat for bopping him upside the head while he's sleeping, but it's not allowed.
I have a mental picture of a de-clawed cat just walking up to the dog and smacking him on the head...I can even hear the sound the paw makes upside his head...makes me giggle cuz cats have such attitude....but the dog must be thinking 'that cat is CRAZY!'...