I think your depth’s going well, you have at least six layers, and the perspective is good as well. What I noticed, as you said, overall similar values, yet also the colors are nearly the same, like his green jacket is basically the same color of everything around him. I gave him a red jacket and hat (with some green added in the shadows and you could add some red with the mandrake’s shadows also), the complimentary of green, which really boosts the contrast and, considering they are complete opposites, enhances the struggle between him and the plant life.