Would anyone know how to get the full information during a workout from the running index iq app, without connecting your garmin account to intervals? It is written to the fit file I believe so should be able to get it, but I am a tad clueless on where to begin 
If it is written to the FIT file as a dev field:
Go to Charts menu - Custom Streams
Click Add Stream and then search the field in the dropdown
Now again from the Chart menu, click +Chart and search for the name of the custom stream you just made. It should be available just like any default stream of data.