Depends on where you got cut in half. Above the waist you have high constitution. Below the waist you have low constitution. If you're cut in two vertically as opposed to horizontally then well that's just silly analytic and you should spend more time stacking Pepsi cans than analyzing stuff like this.
Now for the second question; Why do Arkanian Offshoots only live to be in their fifties? Like, I can understand the Human variant not being able to live as long, but what about the Sephi varient? They live longer than both humans and Arkanians.