I still think the pause is a bit too long between breaths. When I breath naturally, there's really no pause; I'm either inhaling or exhaling. Even though you made the pause between breaths much shorter, it's still there, hence he still looks like he's holding his breath a bit.
Quick edit, just deleting all the extra frames you had around your fantastic animated bits. =)
Of course, now he looks like he's breathing a bit too quickly (maybe he saw batman, and now he's all flustered?), but you can fix that easily enough by slowing down the animation, and maybe doubling the frames towards the beginning and end of his breathing cycle, to give the feeling that he's slowing down towards the end of his inhales and towards the end of his exhales.
The last edit was a big step in the right direction, though. He's looking really cool!