The belt tension looks ok.
My advice with the spring is that if you are at all unsure of it either replace it with a new one
or remove it completely, it does nothing once the pulley is tightened.
I had a loose spring jump off and pierce the cambelt once, it was going around and around on
the belt lol.
Maybe I can't see it in the video but should'nt there be a mark on the crank pulley that lines up
with the 'dot' on th engine. The crank orientation looks right though.
Always turn the engine over at the crank pulley.