I'm sorry about what is happening to your father. I do have a few observations that may help. 1. If he already has had three strokes, chances are good he will have another one at some point. If you observe anything strange that might indicate another stroke, rush him to the hospital. They have drugs that can prevent further brain damage if the stroke victim is treated soon enough. 2. If your father is experiencing problems that cannot be explained by the strokes, consider having him evaluated for Alzheimer's. I know a family that is taking care of someone where the strokes and Alzheimer's are going hand-in-hand with the person they are taking care of. I do hope the "only" problem your dad has involves strokes. I don't mean to scare you -- just consider that Alzheimer's may or may not eventually become a factor. Nowadays they have drugs that do improve an Alzheimer patient's quality of life especially if the person is treated early in the disease -- it's better than it used to be but there is no cure.
I hope this worst-case scenario is something you never have to deal with. I only mention it because I have seen it happen. In the event of the worst-case scenario, there are things you can do to improve (not cure) the situation. I'm not a doctor or anything -- these are just things I have observed.
His father had Alzheimer's too, so that's a distinct possibility.