On a random kook, just go Gracie Jiujitsu 101, with the double underhooks to leg trip. Usually double underhooks are a solid way to go because even if they go wrong, usually something good happens. Except on a really good wrestler. On a really good wrestler or judoka, bad things happen when you hold on.
As for getting out of the scarf hold, I couldn't see how he was controlling your arm away from the camera. The simplest move is just to get your inside arm underneath his body so that you can start to take his back. When the size difference is that dramatic, that's immediately what I am looking for rather than trying to setup some perfect sweep. Because on a dude that big, it would have to be a perfect sweep to get him over.