First of all, for the Hanyuu potentional thing, take a look at my post here:
http://forums.animesuki.com/showpost...1&postcount=37
As for the Satoko aunt thing, it's really subtle, but I guess it's one of those things that doesn't really need to be cleared up.
As for the whole resurrecting thing, I don't think it's a plot hole. Whenever Rika dies, she returns in time and gets to "re-live" her life again, but since many things in the world are affected by chance and probability, every time Rika "re-live" her life, the world around her is played out differently. As a result, from Rika's point of view, each new life effectively takes place in a "new world".
As for the "old worlds" that Rika left behind after her death, well, they may continue on, but since they're no longer OUR world anymore, we (that is, us players, as well as Rika) don't really have to care about them anymore, other than remembering and learning from the things that happened in those "failed worlds". (Best example would be Rika remembering herself getting tortured to death by Shion in Watanagashi-hen, that's why when she found herself heading down the same path again in Meakashi-hen, she chose to suicide (stabbing herself in the neck) rather than getting tortured to death again)
The one ingenius setting in this was "Rika can't remember the final moments leading up to her death". As a result, Rika could never find out who was the person responsible for not allowing her to live past June 22nd.
Rika's experience is kind of like playing a video game on TV, and then turning the TV off while leaving the game running. 1 minute later, you turn the TV back on, and you find your character standing at the last savepoint. The only thing you know is "I died", but you have no idea what killed you and how, and the only clues you have are the events that you saw occuring prior to the "blankout". And, as Rika mentioned, even with those limited clues, she still tried doing her best to survive. But no matter what she did, she always end up back at the "save point" again with no idea how she died.
The only way for Rika to survive is to find out about the mastermind (which we found out in Minagoroshi-hen) a while before her eventual death. If she can do that, then she'll be able to remember it.
Now, as for this "resurrection & memory retainment" phenomenon itself, we have no natural explanations right now. It's as unexplainable as Hanyuu's existence.
Keiichi and the others remembering "broken memories" from the previous chapters, as shown in Minagoroshi, may be a sign that something's changing. After all, Rika's running out of time.
Either way, at this point, it's probably a better idea to just wait for Matsuribayashi-hen, rather than trying to make sense of all this by ourselves.
If you get bored, you can always look at
Shun-san's Matsuribayashi-hen prediction manga for a good laugh ^^:
http://good-for-nothing.sakura.ne.jp.../page/r16.html