[RichardJ]

The best I can tell from your photos and video, the belt is making contact only between my blue lines. Between the water pump and fan and the water and air they are pushing, you are going to need more belt contact area. Aluminum pulleys tend to have less friction than steel. The alternator needs to be lower. A longer belt will let the alt swing out more, but may not give more belt contact until it is swung WAY out.
An electric fan or a clutch fan are alternatives that put less load on the belt.