The fact that barking and snarling when you are not there may be a sign of stress and anxiety. Due to the fact that the dog is too dependent on you and becomes nervous when you are not there.
Dog barking and snarling sign of stress
This I say on the nose. To really understand the situation you should know the history of the dog before being adopted. was being mistreated?
- Did the dog have a mom or was you abandoned when you were a few days old?.
- Did he have other owners before you?.
All this together with the observation of the dog and your behavior with him allows you to identify the problem. Then you can establish a line of intervention aimed at involving other family members in the care of the dog. This helps to reduce anxiety the animal. All this should be done with a professional and not here on the internet.
The fact that he does not stand guard depends on the nature of the dog
There are dogs who are hypersensitive to noise and territorial stimuli and others who are calm. The kennels are full of dogs bought to stand guard or for other reasons which later proved unsuitable for the task because they had a different character from what was wanted. Some time ago I was reading about a dog who was abounded and welcomed in a kennel. The dog was a sleepyhead. And not very responsive to stimuli. Generally the setters are not like that. So she had been bought as a hunting dog but did not have the personality for that task. It happens.
Your dog is what it is, you can only accept it
The fact that he sleeps in your room is not a good idea. I did the same with my dog and saw that when I moved the dog’s bed to another room he took confidence and assumed more autonomous behavior. This is because, despite the current fashion, dogs need their spaces to feel confident.
I also understand that you should involve other family members in dog management. Allow to take him out and feed him. If the dog does not eat patiently, remove the bowl and ask your sister to put it back after 12 hours. So he gets used to it and becomes less and less dependent on you.
Although, I repeat, all this should be done with a professional in the sector.
Then I don’t know it’s difficult to say from here. Surely barks and snarls are a symptom of stress mainly because they occur only when you are not there.