Does anyone know how to read metadata such as fstop (iris) and lens used, focal length etc. from a video file?

Typically you have to play the video back on the cam itself and there is usually a setting to show this on pro or prosumer cams. Not so much on consumer cams.

These values can change with every frame so it's not like stills where each file is a single pic. But there are likely plug-ins that would work in your NLE to show this data.