Wut?
First thing you do is get important things away from the business end. Not getting shot, especially in the head, trumps other gymnastics whatever disabling the gun means. LOL this guy's AR 'disarm' has "Bow to your Sensei!" written all over it, as does pretty much everything else. The one thing he gets correct is simultaneously moving his head and deflecting the direction of aim in that first pistol vid posted. Goes downhill from there and I completely agree that his disarms suck and will get him shot.
Regarding what you train for- depends on your lifestyle and where that lifestyle may take you. I'll say this- as a country we have really turned to shit over the last 10-20 years and inner city crime is heading towards slums of Johannesburg and Sao Paulo levels. Compare the city centers of just about any major international city vs. that of New York, and your expose level to shitbirds is essentially zero vs. 100% in NYC. Situational awareness is your best asset