Also on that last bit, with the training and whatnot for the two months, my wife pointed something out last night about Shouichi's statement on why they can only beat Byakuran in that time frame, too. (Time frame being the battle turning point, as you said.)

Because Byakuran can communicate, so to speak, with all his parallel selves, every time Shouichi went back to the past and changed something, his future self would already know he changed it because he could communicate with the other world and have the information handy to change it to his advantage.

However if the Vongole from the past came into the future and plotted and ployed and trained during Byakuran's "present", he has no way of knowing the outcomes via the parallel worlds. If they trained and tried to defeat him in the past, he'd be prepared for that already because he would know it since they'd be training in the past, as fuck confusing as it sounds.

MAN. SO COOL.