I enjoyed the touch of humour with the axe man walking past the garage in part 4. Well, I am assuming the humour was intended as what else was he up to?
In my view, Oscar is a goner. Think of the Nillson song at the end. "I can't live if living is without you". Heartbeat is finished so Oscar has lost his 'raison d'etre' so what would be the point of his survival? I would like to think that he is still alive however, so that he can enjoy his retirement as he has been a very busy man over the past 18 or so years!!