As woodworker I am reluctant to tell you anything less than to do (or to have it done by a quality woodworker) a complete restoration. It is obvious that there is a failure of some of the glued joints (end grain to end grain) along with some damage to molding. I suspect that the joints will continue to deteriorate without the complete restoration. Short of that, as long as the door feels solid, has no issues fitting the frame, etc. there are some products specifically marketed for architectural restoration by Albatron that you might want to investigate.