Thinnen and Earthpunch sound great. Sandwhip has a nice concept but it seems too much like Torrent (it's basically a sand version). Sandspout to me is really not needed. I understand how it could be useful but there just does not need to be anymore spout abilities. Air and water have similar spout abilities with slightly separate characteristics, and that seems pretty legitimate. I think that, although these abilities can make sense, they can ruin the diversity of the different bending styles. I like how players need to think differently, move differently, attack differently with different elements; that makes it feel like they need to be treated differently due to their different natures. Some of these would make sandbending a lot like waterbending, and that just doesn't seem right in terms of Minecraft gameplay - I just can't see it as appropriate.
I will still say that I like these suggestions, as they are certainly useful and entertaining prospects, so nice job on that.