I think that splitting twins is sad but at least they wont really miss eachother since they never really knew eachother, and they can still be good friends if you mated your tama with a friends tama, the whole one tama after another is really messed up since it gives tama haters a chance to kill one tama after another, but that's not a fact that all tamas and their caretakers must deal with. The poop thing is not cruel, just grose.
I think that the worst on the list was the matchmaker thing, since if two tamas really love eachother they still almost never end up together since the matchmaker takes everything into her own hands, and as a caretaker it breaks my heart since I can't possibly know who my tama really wants to marry, so I think that's the cruelest part of a tamas life.