So I just watched the Everything video - what, no shots of the entire bike? Any dents in the tank/cracks in the sidecovers?
Here's the bottom line. If the tanks and sidecovers are good, you probably have $200 in resale value right there. If the seat has no rips, another $80.
You can part the bike out and make most/all/more of your $800 back. If it runs, or is close to runs, and the electrics all work it looks pretty decent.
I paid $400 for my 1976 CB550F and it didn't run, didn't have good paint, cables weren't connected etc.
When checking electrics, check the following:
Front signals, headlight and tail light should all turn on when the bike is running or key is turned to start. Front signals are two-filament bulbs - running lights and turning.
Signals should of course all work
Horn
Starter button
Brake light (check front lever and foot pedal)
Hi/Lo beam for headlight
Rust in the tank?
Inline fuel filters on lines (nice to see if the previous owner took this precaution - no penalty if they didn't, but bonus points if they did)
Condition of rear sprocket teeth? Do they look like shark's teeth (if so, new sprockets / chain needed)
Any sign of burning oil or leaking oil?