[Southern California] Floating ground on outdoor outlet

So I had my panel upgraded almost 2 years ago. It seemed to have gone well until this past week where I discovered that one of my outdoor outlets has a floating ground. I checked the plug with my multimeter and it was

• 120V between Hot and Neutral
• 90V between Hot and Ground
• 24V between Neutral and Ground

The panel end of the wire has the Hot landing on a 20A breaker, the Neutral is on the Neutral Bar, but the Ground is just in the conduit leading to the panel. I'm pretty sure the electrician had trouble getting the wires back into their spots after the new panel was put in.

So here are my questions:

1. Are there other solutions to this problem? I am planning on pulling new Cerrowire 3-wire solid 12AWG THHN. I can't get enough of the ground to make a connection in the conduit body (I'm not sure if that's even legal) and there isn't enough space in the conduit itself for any sort of wire or lever nuts (also probably not up to code).

2. How hard will it be to pull the wire through the conduit and should I use wire lube? The run is about 60 ft (I bought 100ft). It's buried conduit so I'm hoping on the outlet end it will be a slower 90 and pulling it shouldn't be too terrible but I've never pulled wire before.

3. How hard will it be to get the wires through the 2 90 degree turns? This is the part that I'm worried about since there won't be a lot of space to work with.

You can see the picture of the panel end with the album linked here -- https://imgur.com/a/U4mrKp5

Thanks for any advice, tips, etc.