After seeing your movie, let me play devil's advocate for a sec.
I'm not sure that you WANT him to stop jumping on the gate. If he's dead serious about keeping people out of his yard, then his jumping on the gate will absolutely convince EVERYONE that they do NOT want to go in your yard.
OTOH, if he stands away from the gate and bark, they might think that he NOT as serious as he is; and then they might chance opening the gate and get eaten alive.
Jumping on the gate might be noisy and annoying, but nobody ever got bitten by noise.