That is why adoption is not for everyone. You have no idea what the dog's history is and/or if the shelter even knew or tells the person adopting the whole story, or the shelter personally are not educated enough to evaluate the dog properly.
From what you describe of his actions. The shelter SHOULD have been able to see this behavior first hand and evaluated the dog correctly before they let anyone adopt it. I see shelter all the time where getting the dog adopted out trumps telling about any and all safety problems the dog may have.
You have to ask yourself.
Do you really want to spend the rest of your life with a dog that is a fear biter? Do you want a dog that you have to sedate to be safe? Were you planning on taking this dog RV'ing with you where people and loose children are all around running in close quarters constantly fearful that he is going to bite someone? Fear biters do not give a clear heads up alert before they bite like an aggressive dog does.
I work with last change behavior problem dogs. Just going to a class or getting advice from untrained dog trainers will not help you or this dog. It takes way more than a six week class. It is NOT a quick fix. You will end up with a dog liken to having a loaded 357 magnum. You will have to be on alert at all times so he doesn't bite someone.
Don't be a hero just because everyone else says to keep this dog. IMHO I would return this dog. And I don't think anyone should think less of you if you did.