You might want to look at Golden Cheetah, which has a lot of metrics. You would have to download each of your FIT files and then load them into GC. It’s free.
Strava has a free option and is only $59/yr otherwise. I recently installed Golden Cheetah. Lots of info there for sure, but I need to read some of the docs to understand more of what I am looking at.
There is free plug in called Sauce that works with the Elevate app for Strava. I see all kinds of levels of power from 5 seconds to 30 minutes. I know Elevate works with free Strava because my wife uses it. Not sure about Sauce.
Thanks for mentioning that. I lost track of that project at some point when it had a different name. And Elevate isn’t working with Firefox yet, anyway, so I’d have to use a different browser to Elevate/