

There are kind of two different questions here.
First of all yes, humans are pretty good at telling whether someone is looking them directly in the eyes or not. So if you were to ask someone directly whether you are looking in their eyes or some other part of the face, they would probably be right most of the time.
The second part is whether they would notice it consciously without bring asked. That’s a little trickier. I suspect if you were staring directly at some other part of their face, people might get self conscious (do I have a zit? Is my nose that huge?) But looking at a spot between their eyes, or shiftng your gaze periodically would probably fly under the radar.
Like a lot of people have already said, people are complicated and contradictory; they are rarely one thing.
So you can judge him for, and learn from, the way he has treated other people, while also being grateful for the love, respect, and good parenting he has shown you.
Another aspect is that people often make mistakes and grow from those experiences. It might help you resolve some of the dissonance to talk to him about those things. Many people have experienced that having kids radically changes their priorities. Some people are fiercely loyal to a few people, but couldn’t care less about everyone else.