moleMILKy_try avg bitrate to 18000 and 2-pass encoding. bitrate is the most important setting of all, you can try and change it to something even higher like 24 000 but that is probably too high for youtube anyway.
I can't upload the clip to youtube, but just watching it in a video player it looks good. I took like 2 hours to encode that 30 sec clip though, and I don't think it should take that long. Also, I don't see how low bitrate could be the issue since I tried recording a video using beater's method. I think I actually got some decent quality when I recorded with very high fps + motion blur, why is this and could it explain why everything else looks terrible? I will experiment more tomorrow.
try 12k bitrate