Young Percy on his leash/lead

This was not a successful attempt to allow the wild Percy outside where he longs to be. He runs way to fast for me or for his supervisor, Gracie Twinkle-toes.
He climbs and chokes himself.
So, each day I will give him 2 to 3 minutes of training.
I think he is too young to go outdoors but he is constantly sneaking out if a door opens. And he is envious at GT-t going in and out as he pleases. 
(She is well-trained to stay on the property. Percy hasn't a clue as to what property lines are)