Sounds like an exhuberant puppy to me. You are saying he is play biting which is pretty normal in my opinion. I would let them work it out and not interfere. When the older one gets fed up, I have a feeling he will be put in his place.
I cannot believe that putting him on his side at his age is going to register, but hey...I could be wrong. It does not sound like he is doing anything but trying to play....that is what they do...I have one that is not quite two who still does it...he pulls on the other one's ears. They rip and run all day long. When someone gets fed up...they let him know and it stops.
Just my two cents. Hope it is worth something.
