I can offer you a "hmmmm" about this issue...
the main question: are the artists that painted the first 3 images still alive? if not, are they somebody with big names that could get you in trouble?
generally speaking, if I were the original artist, I would not want my art to be used in derivative works, and I explicitly state that in my bill of sales for my limited edition photos.
ethically, if the original artists are OK with it, or unavailable for comment, I would give them at least big credit for their work, and clearly state that this is derivative work, not original work.
I understand what you're saying, but this was not done for sale or exhibit, only for a specific critique. And it appears that nobody understands the point, so I guess that's that.