In my house, this level of growling at humans would be completely unacceptable. If he growls at you in your bed like that, there is no way that he should be sleeping there. Everytime he gets to stay, it confirms in his mind that growling works.
I completely agree.
The water bottle is great when it just sprays them from out of no where and the basenji just doesnt like it. Very effective to discract bad behavior and redirect with something else. I think in this case you may need to establish your territory - your bed or your furniture.
It is important to establish communication with your basenji at this point.
Basic training will teach you the skills which will give you confidence in your approach to your basenji.
Keep in mind this is a 20lb dog.
He wants to be in the bed because he wants to be part of your pack. I have never met a basenji that wants to be far from their owner. It is natural for them to challenge for the alpha position.
It is important that you learn how to assert your dominance as pack lead in the healthiest way possible and in a manner that can be consistant over time.
I always give my basenjis an opportunity to do what I ask first. If that doesnt work- I just move them to the command I was requesting. If that doesnt work I will soft muzzle or put them in the kennel and they dont come out until they are quiet.
You are the only contact your basenji has. You are their life. You create the environment they live in. Make sure what ever technique you find that it is something that is enjoyable because training is pretty routine in the life of having a pet. Training can be fun and I always have a happy basenji with loving time after we have to go through something challenging.