yes... I have the same question.
WTH is the ending trying to say? what does it mean?
It seems to me that the "eden" they are trying to reach only exist with "pure heart" and with the help of the flower girl.
I totally agree with you that everyone died (or it seems) at the end.
I got to re-watch the TV series again.. it has been a few months since I watched ep26. and now.. i got see if I can find the OVA. =|