TooMuchCoffeeGuy  

My wife has been complaining about my communication skills, she insists that if I must reply with a grunt to at least develop a system to indicate a positive vs a negative grunt.

That would defeat the purpose of the grunt. It is the male equivalent of a female talking. When you say one thing, you mean something else, but only sometimes.

And one thing never means the same thing the next time you say it. And if ever you do say what you mean, you don't make any sense. Now they know how we feel.

She also feels eye contact is best established above shoulder-level.

If she doesn't like you doing that she shouldn't have introduced you to her niece.