Sometimes we have to think about what you are posting before we can give any advice....

Like you I have a deaf cat with no sense of volume control who likes to meow at the top of his lungs. I don't know what you have tried in the past, but I have found that putting a night light in there (in case she also has problems seeing) and having a window he looks out of and can watch the world go by.

Like you, he would attack a number of the other cats so that is why he has his own room. Usually for at least a couple hours every day I put the cats he fights with in a room and let him out to wander the house. That way he has time to sit on my lap and interact with the cats he doesn't fight with. But I leave him out for a few hours and then put him back in the room with a "treat" (usually canned cat food). Connor (my guy) is only about 12 yo, so he is not senile but he has many of the other problems you mention. I know that once I spend some time with him, he always does much better. Even if I am just sitting in the room reading a book while he is there.