Easy to figure out, tough to do.
A deck of cards comes pre sorted, and it's possible to "shuffle" a deck without disrupting the order. That's the type of shuffle he does the most in that video. WHenever he does riffle the deck, you'll see him taking a peek at the cards so he knows what order they're mixing.
As for the cutting, when he collects the halves of the deck, he doesn't let them completely line up. Then he does his 3-block walk, each time flipping the halves over each other. An odd number of flips after the cut will return the deck back to the way it was. The last guy to cut almost put a wrench in his works by aligning the halves, but he managed to stop him before he lost the split.
Lots of practice needed for this, but it relies on basic card handling tricks.