Is sucking in my nose by inhaling a good indicator of how narrow my nose can be made in African American rhinoplasty? (Photo)

I would say, "No", it is not a great way to predict. It narrows the upper lateral cartilage area, not the bone. Closed is certainly fine in you provided it is, of course, done skillfully. Your most important maneuver will be to raise the dorsum. This will change your profile and give an illusion of narrowing the nose. Your tip, while large, is not super-large, so can be altered predictably through a closed technique. Lastly, alar reduction should complete the change. Good luck!

Thick skin can be an impediment seeing a very refined result in an African American rhinoplasty. Osteotomies of the nasal bones are performed to narrow the bridge line.  Suture techniques to the lower lateral cartilages can narrow the tip with some limitations regarding thick skin. An alar plasty can narrow wide nostrils.

I don't believe that inhaling forcefully to collapse the alae does a great job of approximating what surgery can do although it make de-emphasize the width of the alae. There are many highly respected nasal surgeons who favor the closed approach to Rhinoplasty. As long as he/she has convinced you that they can accomplish what you are looking for then you are more likely to be satisfied with the results. Many of us favor the open approach when significant building up of the nose is indicated. It seems like he is very experienced so hopefully this will not be an issue. Best of luck  Dr Harrell