Robert, it sounds like your device is recognizing another faulty battery and is no longer going to let you boot up the device until it is replaced. (Yes it could be a bad part) The only other thing you could have done is damaged a component around the batter connector. (Unlikely, but a possibility)
Sounds like the typical "audio ic" component failing on your device. It either starts with your ear speaker failing or your charging port not outputting audio. This is a repair that require someone that knows how to solder. If you want to ship your phone out i can get you in contact with someone that has done a phenomenal job with all the work i've sent him thus far. (Touch ic, backlight filters, audio ic, etc)
Your first hurdle will be getting your hands on the rear glass of such a new device. If you can find someone that can source the part the second hurdle is price. It will more then likely be an expensive repair considering the device was just released. iPhone 8+ and iPhone X rear glass repairs are ranging from $150-200 USD