Either you don’t have the battery connected, or your battery is faulty! Try unplugging then replugging the battery connector on the joy-con and see if that works! It could also be the connector for charging the left joy-con, try unplugging then replugging the connector on the switch itself, as well as inspect the cable/wire for both battery on the joy-con and charging cable for switch!
There is a possibility Windows has sent you to a default acct! Try logging in again but make sure you're connected to the internet. About your data, if you go into file explorer and into you C: drive (or whatever letter is assigned), you should find a folder called “windows.old” This is where data should be kept.
That would not be a good idea as if you had issues with the SSD, it might be failing and you risk losing data if you continue to use it. If you buy another SSD, you can certainly use it as external storage! You just need a connector to connect the SSD to your laptop, I have left you a couple of links to what you need if you choose to go down this route! https://www.amazon.com/StarTech-com-SATA-USB-Cable-USB3S2SAT3CB/dp/B00HJZJI84/ref=sr_1_2_ss...-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWV... https://www.amazon.com/Seagate-BarraCuda-Internal-Drive-2-5-Inch/dp/B07H28QRKN/ref=sr_1_3?keywords=l...-3
Your disk drive or the disk itself might be bad, check to see if there is anything on the back of the disk (Dirt, grime, scratches, etc.) If it isn’t the disk, your disk drive might be bad, or it is dirty. I wouldn’t recommend attempting to fix the disk drive or tinker with it as you want to have the best chance of survival if it is indeed dirty. You can try buying a cleaner for disk drives and clean it just to make sure it’s not broken. Link below for cd drive cleaner. Unfortunately, you can’t replace the disk drive as it is paired to the Xbox itself (Like the iPhone Home Button.) Contact Microsoft to possibly work out a solution if this hasn’t resolved your issue. https://www.walmart.com/ip/Endust-For-Electronics-262000-CD-DVD-Blu-ray-Game-Console-Lens-Cleaner/23204473
It sounds like the battery you have installed is worn out and bad. Consider getting a replacement battery for your tablet. Use the guide below for replacement steps! Replacing your battery may increase performance at well! RCA RCT6303W87 Battery Replacement