If you've not loaded anything onto the tablet, then the easiest option would be to do a factory reset. Then skip logging in to your Google account till after changing the sync settings.
Check the front of the chassis on the right hand corner for the wifi on/off switch.
If there's no button, you could have a model that did not come with wifi.
Let Windows Update do its thing. The drivers should restore that way and your sound should be restored. If not, you'll have to head to the Toshiba support site and download and install manually.
Did you add your e-mail address to your profile. You should be able to get in that way.
Having said that, you should still be able to log in using the old phone number, unless you had two factor authentication turned on (that sends you a code).
Packed pixels is a specific solution that runs from a USB port, and as such should work with that Dell.
You should also be able to plug any regular screen into that system using the HDMI or thunderbolt (USB type C) ports.