Greetings @Daniel13,
To change the number of guests your listing can accommodate, go to the "Basics" section below the "Listing" section on the left hand side.
In regards to listing your property as Non-smoking, you have done the right thing in adding it to your rules. I put in my rules No smoking or drugs. The only thing for listing options that has to do smoking is in the ammenities section where you can check off
"Smoking Allowed".
I would strongly encourage you to have a security deposit. It is not charged to the customer but a hold is put on their credit card in case damage occurs. I have not had one guest even mention it. If someone complains about the security deposit, they are probably not guests you want anyway. The Airbnb host guarantee does not cover minor damages like "someone vomitting on the bedding and carpet". If this happens, you would make a claim against the security deposit within 48 hours of your guest checking out.
I hope this answers all of your questions.
Happy Hosting @Daniel13!
Dave
David
Superhost Ambassador ~ Host Club Community Leader ~ Community Expert ~ Experienced Co-Host