Can I suggest that you use a babygate to confine him and also have a special treat that he gets only when he is confined? Mine love a stuffed kong but a special chew or anything lovely that takes a bit of time to get through would be good. If you don't confine him often, thar may be part of the problem...youy might try teaching him to be confined by doing it for a short spell then building up just like any other exercise. Try to release him from the exercise calmly so he doesn't get excited waiting for it, make the start of the exercise pleasurable (give the chew or kong)
Its a harder thing to break the coming in scratching as you probably don't want to teach him to bark to come in instead!
Could you cover the new door with a piece of wood or similar that he can scratch at and just replace it when it becomes too damaged?
Please remember that he doesn't understand why for no reason that he can understand he is suddenly cut off from his pack and left alone!