If a comet breaks up into several pieces, will those pieces continue to travel next to each other in the same direction, maybe re-combining via gravity back into a single rock? Or will they just drift apart?
Depends on how fast they are ejected from each other. The pieces will (more or less) have an "escape velocity". If they are faster than this velocity they will drift ever further apart. Slower, and they will slowly fall back towards each other.
My understanding is that it's unlikely that they would ever recombine into a solid object since the gravity between them is so weak.
My understanding is that it's unlikely that they would ever recombine into a solid object since the gravity between them is so weak.