You are in quite a challenging position. This poor kitten has been shuffled around too many times in its short life, is it a wonder he is behaving this way? First I would suggest you put him back into his quarantine room - for as long as it takes for him to bond to you. That could be two weeks, two months, or even longer.
Go into his room frequently but don't approach him or do anything that could appear aggressive. All you need to do is sit on the floor and talk to him, or take a book or your laptop in with you and read out load. Anything to get him used to your voice.
You can bring a wand toy in with you - see how he responds to it. It may take a few attempts but I think eventually he will engage in play with it. Swish it around on the floor to tempt him to chase it. Once he is fully engaged you can drag it over your legs (if you are sitting on the floor) so that he experiences some physical contact with you. Do not attempt to pet him if he is not willing. One other thing, with wand toys be careful that there not feathers or other small parts that he could easily rip off and ingest as that could lead to a bowel obstruction, and always remove all but the hardiest toys (e.g. Kong chew toys for large breed dogs) from the room when you are not in with him.
Make sure he has a litter box that is large enough for him, and fresh water. I would recommend you not leave food out for him to free feed on, rather bring him his meals twice a day, and remove anything that's left after 30-60 minutes. This way he learns that you are his sole source of food.
Treats are another good way to earn his trust. Try to find snacks that he really likes (most of my cats go crazy over freeze dried chicken or similar treats). He will probably not take the snacks out of your hand right away, but you can place them on the floor near you, and gradually move them closer until he will take them off your leg or out of your hand.
As for the growling - this is a common communication form for Savannahs and should not be taken as threatening toward you unless his ears are flat against his head as well. Slapping with his paw is also a fairly common behavior but having the claws out tells me that he has been stretched beyond his tolerance and stress level for experiencing new and strange things.
Your first goal right now is to give him peace and assurance that he is safe. Along those lines, putting a crate/carrier in the room with him to act as a hiding place can help calm him. A Feliway infuser may also help, although I find that hit and miss depending on the cat. Just remember, his entire world has been turned upside down - more than once, and it will take time and patience for him to learn to trust you. However, once he does, I promise you that it will be an experience unlike any you have ever known before! Please keep us posted on how things go.
