My first question would be: how/why did your husbad get bitten, and how many times. This is a biggie, and until I know what went on there, I'm not able to even guess at where to begin trying to answer your questions.
If the GSD, who's still a puppy at 18 months BTW, has food guarding issues then that's another thing that has to be addressed. If that's where all the problems lie, then that's a quick fix for now - no food left out to guard, period. If there's more to it than that, that's a whole different story. But you obviously need to work with him on this, no matter what.
Getting out of the yard is pretty simple - don't leave him out there. Don't tie him out and leave him there, or you'll have other problems to deal with on top of the food guarding.
What breed of dog is the puppy? What sex? That was very kind of you to give the puppy a home...what kind of heartless person just dumps a litter of puppies in a dog park?!