Does he vomit frequently? I ask because a lot of Wheatens are allergic to wheat, corn, and/or soy; some are allergic to chicken, beef, and turkey, too. I do not know if these allergies cause a dog's stomach to hurt, but sometimes when dogs are in pain, they lash out.
Aidan's treats are freeze-dried liver, venison, or duck -- all free of ingredients Wheatens are known for being allergic to. I don't buy him food at the grocery store, and I read all ingredients and countries of origin before I buy anything for him to eat. I especially never buy food or toys from China.
Aidan acts like he has an upset stomach if he eats a few pieces of stolen bread and the like, so we have a strictly observed rule that no one can feed him any people food unless they check with me first. He is a counter cruiser so we are very careful about keeping the counters clear of food and other items.
I feed Aidan Taste of the Wild, twice a day. I used to mix in some canned food (TOTW, Merrick, etc.) but he now refuses to eat canned food. I mix in a small amount (1 tablespoon) of shredded cheese, or a scrambled egg (2x a week), or 2 T of yogurt, or 2 tsp of Parmesan cheese with his breakfast. He eats his dinner plain, without balking, but sometimes I add some plainly cooked meat and vegetables from our dinner to it.
I have a locking trash can in the kitchen.
http://www.amazon.com/simplehuman-50L-Liter-13-Gallon-Semi-Round-Plastic/dp/B003VWMS5E/ref=sr_1_1?ie=UTF8&qid=1329369793&sr=8-1
Aidan will get into anything and try to eat it, and he is especially fond of trash cans, and paper and plastic items. I think he mostly does this when he is bored. He requires a lot of my attention: play time, training, and exercise. I keep an eagle eye on him, keep the doors to the bathroom and my kids' rooms closed, and frequently check to be sure there isn't anything lying around that he can chew on and possibly ingest.
Outside, I watch him carefully because sometimes he will eat things he finds out there -- rocks, leaves, pine cones. He is very used to me opening his mouth to retrieve contraband -- I have to sweep my finger under his tongue on all sides, too, because he will hide things there. I give him one of his chewies when I take something away from him.
He is so into chewing up things that I buy him Himalayan chews and varieties of bully sticks. He takes them all over the house, and hides some of them, so he usually has several of these items in use a time.
https://www.bestbullysticks.com/
Something I have noticed about Aidan is that he is much easier to manage when I spend time every day just sitting beside him on the floor, stroking him or scratching his back. It is soothing to him and he likes it.
Also, no matter what he does (infrequently he will have an accident in the house or vomit), my response is very gentle, both in my tone of voice and my physical actions. In the past few months, in fact, if something like that happens, he comes to get me and leads me to it, and sits there while I clean it up.
A cleanup tip: I keep a metal spatula for cleaning up after the dog. I clean the spatula with paper towels and dish soap, and then boil it and keep it separate from our utensils (under the sink with the cleaning supplies). It is easier and faster to clean up after him and using the spatula keeps the goop from being spread around further. The only reason I boil it for 10 minutes (soaking it in a 10% bleach, 90% water solution would probably work too) is in case one of the kids decides to use it for cooking. Sometimes I think I am neurotic in that I try to be prepared for things that are unlikely to happen.
I think your dog may be trying to intimidate you, to scare you off, so he can do what he wants to do. Aidan pulls that on me sometimes, usually when he wants to go with the kids on the school bus. I have him on a leash, but I was afraid he would bite me. I switched tactics. I scooped him up and held him in my lap until he stopped, making sure he could watch the kids get on the bus through the storm door. Now he sits and watches without any problem, but he insists that I stand next to him, which I don't mind.
He has never bitten me in anger or to stop me from taking charge in situations like this. He will struggle and snap at me or lie on the floor limply (like a mop) if I try to put him in his crate when he doesn't want to go in it -- and these are always the times when it is crucial he go in the crate (a repairman is here). He is quite strong, so if he must go into his crate against his will, I make sure I prevail, and I am calm, gentle, and determined. (Ordinarily, it is no problem to get him to go in his crate.)
I don't know your dog, so I am not saying you should handle this the way I do. I just realized that (1) Aidan had never actually bitten me (not including puppyhood nips), (2) we were destined for a life of him being in charge of me if I continued to be intimidated because that encouraged him, (3) I don't like being afraid of my dog.
Our vet has an animal behaviorist on staff. They do not charge for the initial consultation. Perhaps it would be a good idea for you consult someone. You do not want to get bitten by your dog or be afraid he will attack you.
A physical checkup would be a good idea, too.
