Before I tell you that I think it's sudden rage, I think I'd suggest taking a leadership role. Some insecure dogs badly need the opposite of what we think. Rather than comforting them and reassuring them that things are OK, they need reassurance that you are the leader and will let them know that YOU are not worried about it, and if you are worried about it, you will be in charge of his and everyone elses safety. In other words, when you tell him it's just the ice maker, you are agreeing with him that there was a noise to be concerned about. So he continues to be aware of the noise. If you never said a word, ignored him completely (No talk, no touch, no eye contact) anytime he startled at the ice maker or the car door, perhaps he'd get the message that if the noise doesn't bother you maybe it shouldn't bother him. And if he can't blow up big enough to get your attention about it, maybe he'll quit blowing up. It's worth a try.
Shared beds and couches are earned, not a right. Any dog at any time for any reason who snaps at you should be banned from sharing those with humans. I would leave a short leash tab on his collar and if he snapped at you again, grab the tab, take him off the couch, put him in his own bed on the floor and don't allow him back on the couch. He must know in no uncertain terms that biting isn't allowed. Again, being soft and feeling sorry for him for years can make him think you'll never be strong enough to protect him, or to take charge, so now he feels like he must take charge of things, which in turn rolls over into just being boss about little things. Dogs don't think like humans. It's not that he doesn't love you, it's just the respect that's gotten out of balance. Think over the relationship dynamics and why he has a different reaction to you than your husband. Also, basic training: sits, down, stay, recall, all those should be in place and made into a fun game. He does a "trick", you reward him. Win Win, you both get something out of it. Pretty soon he's happy to just be obedient because you asked and he wants to please you.
There are many examples of similar situations on this forum. Read through some of these other peoples stories and the answers that follow. You'll find you are not alone. There are also some true sudden rage stories to be found. It's not very common, but it does happen. Nobody can diagnose that over the internet, but for your sake I hope it's lack of leadership on your part because that can be fixed with training. Most true sudden rage dogs end up euthanized.
Your dog is a beauty. Please keep us updated on his behavior and hopefully progress.