Sorry about your dad.
>He has a huge character but apart from that, he has fears, apprehension and he forgets, "he forgets us" even and more recently, the only one who he would listen to, very readily, is my mama. 

That's as a result of abandoned him for a long time. It's not too good to neglect parents. You were too far from home. When I say you are too far, I don't mean the distance but the period you used from that far without even going home. It's not good to stay that long away especially when your parents are in old-age. He will remember your mama because she might be only one they were doing things for long. Thank God you want to stay close to him now and I pray he agreed.