What the heck am I supposed to do about Concentration? At first I thought it worked like the undead: Charisma for Concentration. But it doesn't. So what? Do I automatically fail Concentration checks or does it just work as if my Constitution was set to 10?
You have no Con score. As per the rules for having a non-ability, the modifier is always considered +0.
All that I say applies only to myself. You author your own actions and choices. I cannot and will not be responsible for you, nor are you for me, regardless of situation or circumstance.