Wow!
You’ve really gone over the top with 100 bounces. 10 bounces should be enough for most cases as depicted here: Sky Light | Unreal Engine Documentation
Quality of 2 might and should be sufficient.
Try using more subtle values as the engine will not work that well with such extremes. Check this out (if you haven’t) CPU Lightmass Global Illumination | Unreal Engine Documentation This will give you some “rules of thumb” values for the settings.