My guess is lower. I'd put the correlation at about -.35 to -.45, so that'd correspond to an R² of .1225 to .2025. But eyeballing correlations is hard.

Assuming it's a correction line, I don't think you can tell from the slope of that line alone as the clustering will matter and correlations are finicky. Now, if it was a regression coefficient, that sexy line can be calculated just by looking at it (although we'd want to know if it was significant, lol).

Delete enough data points and it will be 1. You'll only have two data points, but you'll have bragging rights.