The "issue" with strangers I don't see it as untypicall myself?? But it sounds like you have allowed it to get to far? My guy did a low growl at company the first time company came over!!!
That was as far as that ever got! I did "Who Petsmy Puppy or Dog" and I used a muzzle on him for awhile till I could see he was calm. I met people first he was behind me quitely while I spoke to folks. He learned..this is how to behave.
I used a muzzle like this:
A Great Small And Lightweight Nylon Mesh Muzzle
You can't work the dog hard in it! And it's not as secure as a "real muzzle" for not for use with a bat crap crazy dog! The dog can remove but not while you are watching him! It will make you feel better and keeps him from going off! Well I can't bite sooo...
Post 8 has some useful links:
New Dog, Very Challenging
The link on loose leash walking also, if the dog is out in front and the leash is tight...you will "never" gain control of this dog!
Hostility towards a pack member is a whole different story! I would start over let your husband take over some of the responsibility, you could start over by doing something like this?
I just got a rescued dog – what do I do? | stickydogblog
And this also might prove to be a solution?
That's how I dealt with my 'Bubble Dog" aka dog with people/dog issues. And he turned out just fine!
So in my view that is what "retraining" him would look like. If your up to the task I think you can do it! But..if you can't or not sure? Keep anyone from getting help and hire a qualified trainer or behaviourist. No harm in getting help at this point you "do" have a challenge on your hands!