I really need to get Blitzen to stop eating everything on the ground outside when we go out for walks. This morning, he tried to eat glass, it was the top part of a broken alcohol bottle. I took it out of his mouth with a fight, but I think it cut him a little. I've been trying "drop it" and "leave it" but it doesn't always work. And sometimes I also try pulling on the leash when I see him open his mouth to grab something. It makes me feel like I'm not feeding him enough, so I've been giving him more food than I used to and he's gone up to 5 treats per day. What else can I try to stop him from trying to eat everything outside?