It's really painful/impressive listening to D’Onofrio speak mandarin. I don't know a lick of the language myself but even I can tell that he put a lot of effort into actually learning the lines, at least phonetically, and yet at the same time his accent must be horrific. His character's delivery in english is very measured and deliberate, but when speaking mandarin it sounds like he's pausing between each syllable.

Also, as a cool tidbit of trivia, I read that in the scene where Madame Gao reveals that she knows Fisk can speak mandarin and they have a conversation using the language, they actually both switched to Japanese when she asked if Nobu realized he also understood Japanese.

Did he get sprayed with gas or something and I missed it? He seemed to go up in flames awfully easy. I was fixing my kid breakfast, but only looked away for a second

Yes. In the flashforward where the knife first appears they have a clear shot of it being thrown and piercing a barrel, which starts leaking fluid. Then in the final fight, right before he catches on fire, DD kicks him in the chest with both feet and Nobu falls to the ground next to the barrels where the fuel has pooled. The shot also shows the fuel pouring out and there's an obvious audio effect of liquid pouring out. DD ends up on the ground after his kick and starts crawling away. When Nobu gets up his entire front is soaked and he walks towards DD for the final time.