Lolol, are those breasts on steroids or what? And die for having just a 32-inch rib cage, okay?
Aaaanyway. I still don't have any visible growth (or very little of it, at the nipples), but I do have the pressure sensitivity - bumped into a doorway yesterday, ouch. I manage to sleep on my belly fairly well still. My rib cage is huge, so sometimes I just use my lower ribs as a support (I feel like a boat), and it's fine because my chest itself doesn't really support any weight. Not mega comfortable but does the job. But my favourite technique is putting my pillow on my chin and upper chest, "hugging" it with both arms and using it as a support. Almost no contact in the "risk area".
If none of that works, well, sleeping on the side might be something to try. I actually find that comfortable if I can mimic the comfy feeling of the bed in my face and such by hugging something big. A lump of covers, a plushie or a pillow.