I can't help with your problem, but how have you been reporting to Apple? I've had good luck (most of the time) using email@example.com. Although I don't always get personal responses, I have gotten them when necessary and have usually seen the issue get fixed. (In my case, this is usually malware that I am reporting for inclusion in XProtect.)
I found a solution! It works for me, anyway. (This has been such a pain - it took me over two hours to track down something that works) Once you're sure you've uninstalled any previous versions of iTunes, you can download from these links. Unlike the regular download pages, these actually worked. There are 2 links because Quick Time isn't included in the iTunes download here.