The form Wu Tunan performed was the fast form or "yongjia" which means application form (for fighting) passed down from Yang Luchan to Yang Shaohou, and from YSH to WTN. Of course the video was shot when WTN was about a hundred years old, so he did not performed with the low stance. Whether WTN did perform the Yang style yongjia with strong influence from Wu Style taiji I can only guess, since I am not at that level yet (or ever).
Here's a link to a performance by his student. Quite different from WTN's yongjia, but I guessed all the principles are still in there. http://youtube.com/watch?v=l3M98I5Te7Q
As to the "thumbs up", that's the tanzhi, which generally follows the single whip. Basically it's an attack using the thumb.
I think WTN's Mongolian name is Wulabu, the meaning of which I am afraid I do not know (since it's a translation from Mongolian).
There are a few publication on this yongjia (so far I have seen three), but they are all in Chinese. The authors are all WTN's disciples and student (Ma Youqing, Li Lian, and, the third name just slips my mind).
Hope that helps.