When Yukon was that age he did grawl at me when I was near his dish.I would right away give him a stern "NO".When he stopped,I would praise him and rub his neck...I did this a few times..Then I tried to take his bowl away while he was eating.It was a bit of a test.He growled again.Stern "NO" again.He stopped.I praised him and as I was slowly putting the bowl down,I was rubbing the back of his neck..After that I had no problems at all.With Tron,I had no problem...And they are both GSD's.
As for the car and door,he needs to be taught the "sit" "stay" command..It will make things so much easier for you....
