17:05:17.879: base resolution: 1920x1080
17:05:17.879: output resolution: 1920x1080
17:05:17.879: downscale filter: Lanczos
17:05:17.879: fps: 240/1
That's not a good idea.
17:08:31.638: Output 'simple_file_output': Number of lagged frames due to rendering lag/stalls: 2337 (55.2%)
Rendering lag. You're overloading your GPU.
https://obsproject.com/wiki/GPU-overload-issues
17:08:31.639: Video stopped, number of skipped frames due to encoding lag: 2647/2666 (99.3%)
You are completely overloading your encoder.
The 2080 is a great card but I honestly don't think you're going to get 1080p240 out of it in a single PC configuration. Either go for a smaller frame or a lower framerate.
Your files are small because no frames are getting into them.