1. I personally would not recommend smoking anything with your BP in the room. The respiratory system of a reptile is much more delicate than the respiratory system of a human. For snakes specifically all of their organs have to be kind of weirdly set up to fit, lol. I've never smoked so I have no first hand experience, but I've heard that it can possibly have a role in giving reptiles respiratory infections. If I were you I'd try to keep the smoke far away from the little noodle. Maybe I'm just paranoid but I won't even light a candle in the room with my BP.
2. Ceramic heat emitters really do just suck up any moisture... I have one too and it can get pretty annoying. A spray bottle will work great as long as you continue spraying multiple times a day. I eventually started using a cool mist humidifier with a timer on it to regulate my humidity, but spray bottles are a lot cheaper
3. Unfortunately mites can show up later on... My first snake came with no visible mites but apparently there were eggs under his scales... A few weeks into owning him *poof* suddenly mites appeared. I don't think this is incredibly common, but it unfortunately can happen. It's not really that big of a deal, they're just a nuisance to get rid of. Other things that can possibly transfer mites would be things like visiting reptiles at a pet store, going to a reptile convention, etc. If your BP is pretty new I would just keep an eye on him for a few weeks. You most likely have nothing to worry about though!
I hope everything goes well with you and your new snake! And hopefully the new roommate too, haha