Since there is no gun registration in NC (with noted exception of Durham county), it doesn't matter who is the actual owner. If you are not prohibited from possessing a gun, then you may carry one. You also have no need to tell anyone whose it is.
OC in a vehicle: For you, for the time being, I recommend a holster or similiar device that will secure it in the passenger seat (when the main squeeze isn't in residence), or on the dash. That way it's in sight, and secured from flying around. Most of us simply wear it the same in the car as while walking. It will be up to you whether or not you inform a LEO you have it, if you get stopped (is your user name any hint?). You mention 'within reaching distance'. That becomes an issue only if there is grounds for a concealment charge.
There is no actual mag limit, as long as you don't exceed the placarded GVWR for your vehicle.
NC has not limited the mag capacity, unlike some states. I carry 19 rd mags, with one chambered. Some local ordinances post a limit of 20 rds. Some guns, like Glock, can take a 33 rd mag.
Carrying chambered, cocked, safety off, or any combination is up to you. NC makes no distinction between loaded and unloaded guns for offenses. I would say most of us carry in Condition 1. You didn't indicate what gun you have; whatever it is, use a good retention holster, and practice (unloaded and in private) getting it ready for action in any activity or position.
Don't make an issue of the fact you carry, but don't let anyone else do so either.