You ain't getting good quality out of the tube streaming. Your best bet is upscaling your export from 640x360 to 1280x720 and uploading that, since the HD feature makes videos look not so bad.
In order to upscale well, a good filter to use is
nnedi2. Download the zip, put the nnedi2.dll that you find inside of it into your plugins directory of avisynth, and then make an avisynth script like so:
Code: Select all
avisource("your exported video.avi")
nnedi2_rpow2(2,1,3)
Also, I just noticed, but your preview isn't 640x360 but in fact 582x360, which means that in the preview it doesn't show your whole image, and your clip is already like that to begin with.