You're having so many apparent problems with so many different things that it's going to be very hard for anyone to help without being right in front of your equipment. You should find a friend or someone local and trustworthy who can help you in-person.
Many if not all of the problems (like inability to family share and AirPlay) sound like misconfigured iCloud ID settings spread across multiple devices. I suggest going through and reconfiguring everything very carefully, before attempting to use any of those features. Again, if you don't know how or are the least bit unsure, you need to find someone to do it for you in person.
Changing one thing at a time then testing stuff out, like someone over the phone would have you do, is a recipe for disaster. Apple tech support is no doubt trying to help, but you've got too many moving parts here to effectively do it remotely.