What breed? is he neutered? whats he fed? How much exercise does he get? have you been to a training class/ had a trainer/ behaviourist out to see you?

Sounds like classic resource guarding

Get a harness, and a house line, so you CAN remove him from the furniture without getting near the teeth.

 

What breed? is he neutered? whats he fed? How much exercise does he get? have you been to a training class/ had a trainer/ behaviourist out to see you?

Sounds like classic resource guarding

Get a harness, and a house line, so you CAN remove him from the furniture without getting near the teeth.

I was going to say it sounds like RG as well. A house line will be your saviour, but you really need to get a behaviourist in to observe and to get to the root of the problem as to why he is doing this and to teach you how to help him

 

Have a read of the resource guarding sticky

http://www.petforums.co.uk/threads/resource-guarding.279444/

 

Make sure the trainer does not use alpha or dominance theories in their training as that will have a bad effect on the dog and make things much worse.

Have you tried calling him from another room in an excited voice and treating for recalling?

 

As said above, have him on a house line. That's like a light lead but without the handle on the end (which could snag), and is about 6-8 feet long. It just trails around behind the dog. You can then pick up the far end without direct confrontation and lead him away from the situation. It should be attached to a body harness rather than a collar.
Then you make moving away from whatever he was guarding a more rewarding experience than staying there. A 'let's go' in a happy voice, a game or treat when he comes away and does something you ask of him (a simple 'sit' will do).

 

How old is he? What was his background? How do you handle him, in general?

Sounds like he was an anxious dog to start with, and incorrect handling could exacerbate anxiety. (Not saying you've done that BTW )

Growling often dictates that the dog is not happy with a given situation and if punished for growling, then forced into/out of a situation can push the dog further.

 

We don't know anything about his background. Our vet estimates he is around 6-8. When he growls we just say "No!" until he stops. And in general we treat him very well. I give him as much attention as possible and my mom is completely in love with him.

 

Have you had him vet checked to rule out any under lying infection making him pee?