New to this site. A 40 year professional photographer and a licensed attorney specializing in Copyright, Trademark and Licensing (the softer side of Intellectual Property).
Your title alone speaks of good common sense instincts but I wanted to take a moment to highlight several writers who analyzed your legal risks under the guise of Fair Use.
17 US Code, Section 107 Limitations on exclusive rights: Fair Use is a defense available to those accused of copyright infringement. In order to claim the defense you first have to admit that you did, in fact, infringe. Then the four factors within the law, which are very specific, are carefully analyzed with regard to your unique situation and set of facts. One thing is for certain - if you accept money for your work none of the factors apply and the defense is not available to you.
That's the bad news.
The good news is that you can continue your study but you should do it privately. You should not post your study for public viewing on sites like this or your professional web site.
I appreciate that you took the time to ask the question but , if it were me, I would take the series down and only show it to friends and colleagues over a cup of coffee in my home and I would not sell any image.
Now for the disclaimer: I'm not your lawyer. We do not share an attorney/client relationship. My email is in the form and spirit of educating photographers in the often misunderstood application of the Fair Use defense.
I found your photos on your professional web site rich and full. Your clear understanding of black and white photography is evident. Great work there.