Your son is lucky to have a father that loves and cares for him so much. Good on you for being the parent that you are. Also, its ok to be sad he's moving out. Whether he's 2 or 22, he's your son and its understandable that you want him to be around.
On a positive note, it looks like he will be about a 4 hour drive away. An 8 hour round trip is decent sized, but still doable in a day. Remind yourself that you'll still be able to go and see him, even if to just take him for lunch and catch up before turning back around to head home.
Both you and him got this bud!