I really would not let your character design be dictated by pursitic iso rules.
honestly, I liked the very first version of your character a lot better - he looked much more lifelike; what you have now is very stiff.
I mean, who says that a person is always perfectly aligned to the front? Sometimes you may bend your head a little bit to the side or have a small twist in your posture - its those irregularities which make up the human shape.
I would do the following - create yourself a test environment with some iso tiles that are representative for your final environment (not graphically polished but size-wise), and put your character in there. Does he look wrong or right? Judge this with your artistic eye and do not draw perfect red lines to see if everything lines up.
Those tiles could be as simple as a basic grid on the floor.