He seems to be acting pretty much like a normal LGD 5 mo. old puppy. He's not going to want to go for long walks because, like a well-bred Livestock Guardian Dog, his instinct tells him to stay with his flock. His excessive drooling/foaming and his refusal to walk further may well be him stressing out because of this instinct.
However, he is a puppy and if he gets bored enough he will stray, on his own terms (they do tend to be rather independent!).
Probably the very first thing that I'd do if I were you, is to read
Rescue and the Working Pyrenees at the site run by the Livestock Guardian Dogs Association,
www.lgd.org . It sounds like it's information that you really need and there are resources on that site that are going to give you the specific knowledge that you need. LGDs have been bred for centuries to be a bit different than most dogs (you wouldn't want a pitbull guarding your sheep, would you?
) so sometimes that needs to be figured in to how you train them. They definitely DO need training, though, so I'd find out all you can.
LGDs are different to a certain degree from other dogs, but I'd agree yours is probably bored. You could try getting another dog for him to play with, but since your parents seemed to be a bit upset about this one, I don't know that they'd go for it. I agree with DuckyBoy that he's just being a GP (or any other good LGD) and he'll grow out of the chewing and playing stage. The hard part, as you're finding, is just making it through that stage.
I'd try getting the largest size Kongs you can (at least a couple), put peanut butter and dog kibble inside one and give it to him whenever he needs distracting. You want to get 2 so you can be running one through the dishwasher to clean/sanitize it but still have one ready in case of need.
You also need to keep the puppy separate from anything that he can chew on. If he's getting all his "chewables" from inside the house, make him an outside dog until he's past his chewing stage. Many LGDs prefer to be outside dogs; GPs are more likely to take to living in houses but, again, they are very independent-thinking dogs and that makes it very difficult to train them to behave in a house. Make sure that he has not only enough water to drink, but plenty to stand or sit in for when he gets hot. He probably won't lie down in it but he'll try to cool himself off by getting the pads of his feet wet. One of the small livestock water troughs works really well and will last a long time, even if he tries to chew it to smithereens.
My advice is to go ahead and put him in a kennel
near the critters he's supposed to be guarding and keep him in it unless he's out under supervision. He'll tend to watch them and what else is going on if he can't get out and play too much and he won't be able to get into trouble that way. Just make sure that you let him out right around 2, let him blow off some steam, and then (and only then!) put his food inside the kennel and lock him inside to eat.
LGDs tend to be more active at night (when predators are around and the boss is sleeping), so feeding him at night isn't cruel at all; it's normal for them. If you feed him in the morning, he's just going to be revving up with nowhere to go. If you've had him run off a lot of steam and them feed him, he's more likely to settle down and maybe even have a nap. It might help avoid big barking scenes when you leave him to go to bed. Just make sure that you also clean up the poop from inside his kennel every day and that he has shelter from the sun. You can even take a regular chain-link dog kennel, stretch a tarp over part of it for a dry, shady area, put the water trough in a corner, and put the chew toys inside.
You might also put in one of those big indestructible balls inside, too, when you can afford one. He can bounce one of those around the kennel for just about forever without losing it or breaking it. You can search online and find them a lot of time at places that supply animal rescue groups, if you can find any locally. If your parents believe that the dog can't get to their belongings to chew them up, they might also step in to help you buy something to keep the puppy happy, too.
Regardless, use your imagination to just change out things in his pen every day or two. Try taking some pumpkin (doesn't really matter what kind) and freezing some in big chunks. Give it to him as a treat when it gets hot. You can do the same thing with yams. It will help him teethe and also keep him occupied. Talk to people in animal rescue groups in your area, too. They are almost always really nice and very, very glad to help someone who is trying to keep a "problem" dog and they've got tons of experience with working with "problem" dogs. They and the LGD online forums may be your absolute best resource! There are some absolutely great dog trainers in this group but it would probably pay off to also chat with people who are experts with your particular type and breed of dog.
Good luck to you, your dog, AND your family! I'm hoping everything turns out fine!

