I think I'm really hearing that you would like to take the opportunity that moving to go to grad school offers as a way of ending this relationship. I think that is a great idea.

Sometimes the kindest thing to do for someone doesn't appear to be kind. Think of the mother bird pushing her baby out of the nest so it can fly and live it's own life. Freeing him from what appear to be a dependent relationship with you would be very kind and possibly life-changing for him.

Congratulations on your upcoming grad school !