Ouch! I'm no expert but It definitely doesn't look safe or okay. Especially the back bend. In the one video with no shirt when he stands back up there is a awkward bulge in his back as he gets back upright ..can't watch anymore I'm not a fan of seeing things like this.
Whoa - my son did a lot of yoga early on - so he is flexible. But honestly the thing that bothered me most was the ab workout with the weights! (But I didn't watch more than 2 of the videos). Hope those mattresses protect him on those marble floors!