Hard to say on the rotation. That doesn't seem like too many miles on the chain but every situation is different, the amount and type of dirt and slop that gets on your chain, the frequency and how you clean the chain and how you lube the chain all make a huge difference in chain life in my experience.
At 800 miles on my 2018 TL CC I rotated the chain at about 0.45%. I clean my chain and drivetrain frequently and try not to shift under load and I ride alot in the forest where the dirt isn't as bad as desert or other gritty places.
I usually use this as it is easy and quick:
CC-3.2 Chain Checker
When I use calipers this is how I do it.
1) set the caliper at about 5.6 in to slide it in the link openings.
2) insert the inside measuring jaws between the chain rollers.
3) extend the jaws to tension the chain and record the measurement
Measurements rounded up to the nearest 0.005"
new chain = 5.715"
0.5 = 1/2% stretch/wear = 5.745"
0.75 = 3/4% stretch/wear = 5.760"
1.0 = 1% stretch/wear = 5.775"