At your own home, your dog was in his own territory and your son in law was just a visitor. Your dog was comfortable in his own place and thus could be friendly toward your son in law. Even if you were visiting at your daughter's place with your dog, your dog was not "living" there and thus was himself a visitor and thus establishing visiting behavior.
Now when you came home to your daughters house, your dog recognized that you are not in the best physical shape and was recovering. As a result, he has gone into protective mode. Canines in the wild often will push infirm dogs out of the pack thus being sure a sick or injured animal doesn't affect the packs ability to hunt and survive. These behavior patterns are seen in domesticated dogs as well from time to time. As a result, a bonded dog will protect his human when they are injured or ill if they feel there may be a threat. Since your son-in-law is likely the boss of this household, he would be the likely one you would need protecting from in your dog's mind.
Now to correct it will take some time and it is good he has had training. That will help. If it is possible, have your son in law work with him a bit on obedience training rewarding his obedience with tiny hot dog slivers. The following site is helpful in helping people train dogs. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.http://www.schutzhund-training.com/training_theory.html
This training will help your dog see that your son in law is to be obeyed and what to expect from your son in law and not trigger the protection mode as much. It will also establish your son-in-law as your dog's boss as well. As his boss, your dog should not be reprimanding him or trying to control him with barking, growling and lunging. The other thing you can do is keep a leash on him while he is with you on the bed. When he barks, growls or lunges, give a firm low toned "NO" and a short tug on the leash and have your son in law just stand there. When your dog stops the behavior, give him a tiny hot dog sliver as a reward for not barking. If he doesn't start the behavior, go ahead and give him lots of calm praise and a treat. If Sky can enter the room without triggering a response at a certain distance, start at that distance so your dog realizes that not reacting gets him the treat and reacting gets him a reprimand from you. Between that behavior modification training and Sky working with your dog on obedience away from you, the situation should resolve pretty quickly. In many case it is resolved in just a few days. I'm not sure how long you will be in recovery but it will help for any future times you need to stay at their house as well. I hope I've given you great service. If so, I'd appreciate a 5 star rating. The rating should be based on my answer and not any site issue. Experts are not compensated until a rating is done. If you have any other questions at all, please reply here and I'll be happy to follow up with you even after you have rated. .