[Seth]

Another thing that I forgot to mention...

...didn't Harry's patrones take the form of a stag? It showed it in the first scene but in the book the patronus was supposed to travel and chase away the dementors. When Harry goes back in the past and performs the patronus charm it doesn't actually form a stag like it did in the first scene, but just a lot of bright light. In the books he could command the patronus on what to do.