-Even though he is neutered, there had not really been enough time for the testosterone to be flushed from his system, so you are still dealing with the temperment/etc of an intact dog.
-Moses may or may not be an issue. Yes, it does seem like many problems cropped up when M came along, but it is also the same time frame that O would be reaching maturity. Maybe a combination? Maybe the arrival of M, maybe just poor timing. Just because O dominates M, doesn't me that the presence of M is not troublesome for O.
-The bite sounds like it could be O being overthreshold/overstimulated. Playing with a toy, playing outside, kids running around, etc, could put O overthreshold. And it does take time for an animal to come down from an adreneline rush. (more on this, i suggest reading (surprise!) Control Unleashed and playing lots of the Off Switch game)
-Or perhaps the bite was preditory drift?
http://www.alldogsgym.com/content/view/378/
squealing children can trigger preydrive.
that's my two pennies worth of thoughts