The not using the hind legs really concerns me. At 6 weeks of age fractures can be really hard to see and given her symptoms I would recommend re taking X-rays now that it has been some time and see if there is bone damage that maybe was just too early to see.
If she cannot use her hind legs then she does have neurologist damage that we need to consider.
A and D ointment works well, but she should not be having diarrhea as a result of the injury. We need to get her on a feline probiotic and also call your veterinarian back and let them know what is going on. Constant diarrhea is horrible for all involved (especially your kitten). There are medications to help diarrhea in cats that we need to start using with her so her rectal and vulvar area do not get more inflamed than they already are.
I would also recommend looking into veterinarian acupuncture to try and get some neurological function back. At 2 weeks we should be seeing some improvement and since we are not the prognosis for gaining use of her hind legs gets smaller every day and acupuncture can help with this.
My recommendations are that she needs to be rechecked by your veterinarian and re take X-rays to see where she is at ( there are many times in young animals and humans where the fractures are not evident immediately and we need to check for this)
At her recheck appointment we need to get her medications for the diarrhea and discuss how you are going to manage a cat who cannot use her hind legs at all. There is physical therapy to start and you may discuss with your regular veterinarian getting your kitten to a specialist for a consult on what can be done i.e.. surgery, physical therapy, rehab, acupuncture etc.
I am sorry your little one is going through this.