It should fit since the Boulevard is not an unusually wide seat.
As for RF vs FF, you didn't say how old your child is. If he/she is younger than one, absolutely RF it and tell any FA who disagrees with you that a child younger than 1 rides rear facing in their carseat in a car AND on a plane! If your child is older than 1, I'd encourage you to FF it to make it more pleasant and comfortable for the person in front of your child.