score:6
I used to listen to the Vatican Radio podcast which included a recording of the Pope's Urbi et Orbi blessing and they would put a disclaimer in the recording that the blessing didn't apply to recordings, only to those present or watching/listening live. The key distinction is live versus a recording; even if you're watching the EWTN web stream -- which might be broadcast delayed up to a minute or more due to the nature of "live web broadcasts" it still counts as live.
As for how much it counts toward time off of Purgatory, there is the rule in moral theology that you only receive the graces you're disposed to receive.