I think your dog thinks he OWNS you, and is resource guarding, more than being protective. NOT GOOD! It means he thinks HE is the boss in the house, and you are his personal property, and does not want to share you. Not to him to make these decisions at all!! Not for him to decide who in your household is allowed near you. I get the sense that your daughter may never have been very comfortable with your dog from the beginning and he is picking up on that.
Like the others have said, there are a lot of details you mentioned that give ring alarm bells for me - I could be reading it all wrong, but often the wording a person uses to describe a situation does give a lot of underlying info:
First, at 16 months, your dog would be in the age where they start being protective (sometimes). If he has always been protective of you, even from a pup, that was more likely resource guarding - very different than protection and a BIG NO-NO. That means he feels like he is the owner and controller of resources in the house, not you, or your daughter. I think you have a household rank issue here, and that can be fixed, but it does take a lot of work and effort and consistency from everyone.
With the bite in the kitchen, not sure what happened, hard to say if we can't see exactly the details - but I'm willing to give him the benefit of the doubt and say that maybe he thought that your daughter was going to give him a treat (kitchen, food, hand), and he bit her by mistake, thinking she had something in her hand for him? Did he growl at her first? Do you have more details of the incident? If not, again, he might have been acting in a possesive way of the food on the counter.
For the bedroom incident - I agree that reprimanding your dog after the fact is too late - by that time he did not associate your displeasure with his behaviour, so in his eyes you were coming out of nowhere with threatening behaviour towards him - though his reaction was still not acceptable.
One thing that is a common element here is that both times he has reacted to someone reaching out a hand towards him. Has anyone smacked him one in the past so that he feels he needs to defend himself?
Your daughter insists that you get rid of him? How much authority and power does are you giving a 12 year old? It sounds like the dog and the child have way too much power in this house-hold. Not wanting to be mean or critizise, trying to get a big picture of what is going on - and I think there is a big picture of what is going on that needs to be examined, not just the individual bit and aggression incidents. I get the impression that there is a lack of clear, strong and confident leadership in the house, and this is causing problems for both your GSD and your daughter.
Being a strong leader is a way of being, but people can learn. It is not about yelling and threatening, and bullying. Strong leaders are calm, and firm and confident, and inspire respect.
I think you need to practice some tough love with your GSD - start NILIF right away, take away bedroom priviledges. Sorry - that would kill me too not to have my dogs with me, but this is very serious, and if you don't take steps to set, enforce, and maintain a clear hiarchy in your house, you will be in for more issues.
Your daughter does not get to say who stays or who goes in YOUR house - but she does have a right to not live with fear - so I would always make sure that your GSD is somewhere where you daughter does not have to worry about being bitten again, let that be in another room, in his crate, directly under your supervision and control.
And what is this about your daughter coming to you "in an aggressive way"?