If he regularly uses the car he needs to be listed as a driver even though he no longer lives with you. If it is primarily getting garaged at night where he now lives, versus your home, the insurance company also needs to be informed of this as they need to change this information on the policy. This can increase or decrease the rate on the insurance policy depending on where he moved as zip codes change insurance rates. Adding him to your policy can also increase how much you pay for your policy.
There can't be two insurance policies on the same car. In New Jersey, as in most other states, the car insurance policy follows the car not the driver. Whoever owns the vehicle, in this case you, needs to be the one to have an insurance policy on it. He can't get an insurance policy on it because he doesn't own the car.
It sounds like he moved out and has possession of the car now. If this is the case and it was my situation I would transfer the title of the car to him. He can then get his own insurance policy on it at which point you cancel your own policy. This removes the chance that his causing a big accident means that the other party can go after you if the liability limits on your policy are exceeded. It would also prevent your rates going up on your insurance policy if he does have an at-fault accident.