[fostermom]

I JUST started reading a book by Jean Donaldson called Mine! A Practical Guide to Resource Guarding in Dogs that you might find helpful. I'm only on page 11 but am already finding info that sounds applicable to what you're experiencing...

Since you mentioned that he seems better with your husband, under Location Guarding one section reads:
"An interesting feature of all resource guarding is that its severity may not only be tied to the value of the resource, but also who is approaching. Location guarding, such as a dog who seems to let the wife but not the husband in the bed, is a prime example."

And since you mentioned he growled at you when you were approaching when he was with your husband, under Owner Guarding:
"Dogs may be selectively aggressive when approached...if they are in the proximity of their owners. Owners often attribute the behavior to "protectiveness". The topography of the behavior is identical to other types of resource guarding."

And the good news:
"...resource guarding resonds well to desensitization and counterconditioning and to well executed operant techniques."

Although I'm not up to this section, it then lists exercises you can do with your dog to resolve this. Might be worth a read.