All cruise lines include food in the fee. They will have multiple venues where you can dine for "free." They will also have restaurants that they charge an extra fee for. You can choose to eat in these or not.
A current trend started by NCL is "freestyle" dining where you do not have to dress up for dinner - I personally like this. Many lines now do something similar but NCL is reported to be the best about this.
Others will know more about this but I believe that prices will go up and down before a cruise likely depending on what bookings are like. I think it is better to book earlier and then, if there is a price drop, call and ask them to match it.
NCL has some singles rooms, I believe on the Epic and then the Breakaway (next year). They are are cheaper for a single than having to pay two fares and they have been getting some good reviews.
Good luck and I hope you enjoy your cruise.