The annoying thing with breathing anims is that i find i always animate them 10x faster than a normal person breathes. Try breathing like the most recent anim, and it's pretty weird. Although of course, it depends how idle he is. But if he'd just been running a mile, he'd probs be on his hands and knees (or at least i would, lol). Basically, i think you should hold a bit longer between breaths, and i find it's quicker to breathe in than breathe out. The problem here is leaving the static frame on hold, which can make the anim look jerky, so then it's up to uber sub-pix anims.
Btw, cool sprite! And the anim so far is very smooth.