Difficult to diagnose, why not remove alternator belt and re try the engine again - at least this will rule the belt out.
It seems to be running on 4 cylinders so doubt is an issue with valve train unless you have a tappet that has loosened and adjusted itself to a large clearence - doubt this though tbf.
May also be water pump bearings colapsed but i would be sure you would have water pissing out if that was the case. It is worth taking the top cam belt cover off (2 x 10mm) bolts and having a look to see if cam pully is catching the cover at all. Also cam belt tensioner wheel may be dry and worn out, again doubt it because that noise you have is pretty loud.
Sorry can't think of owt else right now