I know this is probably a bad idea but I decided to schedule a connection in Shanghai (Hongqiao), arriving ~4pm and departing ~9:30pm. I haven't been to Shanghai in a few years and there are some sites I want to see.

A few questions to help with my planning and whether I go ahead with the connection.

I've heard that the taxi queque at Hongqiao can be quite long. Is this consistently so?

Any idea how long it will take to go back to the airport from the Jing An Temple area and the area around Xujiahui at around 8pm on a weeknight?

Lastly, I plan to check in for my onward flight before I leave the airport. How long does it take to clear security at Hongqiao these days and when does the gate close for boarding? I will be flying China Southern.

Thanks.

Yes, it can be long, but there are 2 good workarounds:

1) walk ~200 meters with the traffic. Once you get to the first traffic light, all taxis are fair game.
2) take the bus to Jing'an station; very frequent service

Getting back to the airport at 8p should be easy if it's not raining.

I wouldn't bank on this because check-in counters often open 90 mins before flight time. However, you might be able to use a kiosk or do online check-in earlier. The check-in cut off is 30 minutes before flight time and you need to be at the gate by the 10 minute mark.