If you are not using TrainingPeaks then you should give it a try. This would give you a measure of ‘fitness.’
You did an 80 Tss run and felt good the next day. I would say that certainly makes you fit.
You run 10 miles non stop. That would indicate you are fit.
How fit you are depends on what you want to accomplish. I want to climb 14,000 foot summits via easy routes, in ‘alpine style.’ In my view being able to do this would make me very fit, but nothing like people who are climbing Denali. And the comparison goes on as there is always someone fitter. If you are doing a run like this as part of an additional ten hours of training a week I would consider you very fit.
This is all about personal goals and achieving them. Can you do what you want to do?
That’s how I would look at it.
I hope that helps.