What does the image convey about “toxic subjects” (their character, dynamics, etc.)? (How) Does this image open up the concept of “toxicity”?

Toxic masculinity! Toxic humanism! Right on, that's clever, but go ahead and make the message even more explicit. This is where photo alteration can add even more to your work. Look for some of those horrific bullfighting images you see circulating in the PETA circles online. More people should see what the killing of their food looks like anyway. But even more importantly, teach people to make connections between the brands around them all the time and visual association. I'm writing this on a MacBook right now, a machine that came with the image of an apple with a bite taken out of it. I tend to hate all the stupid Christian imagery around me that I have to deal with, but this Edenic reference on my computer got to be a bridge too far. I covered it with a sticker like many a hipster type. Quite the digression, but this is my way of illustrating what work you can do toward building critical awareness about the toxicities in our lives and the ways they mutually constitute one another. Feminist geography might be helpful for you if you want to go further with this - see Doreen Massey.