Hi icthis,
Regarding your first query related to the more than 10 KM 1G SFP requirement, its the first I've heard of this limitation and I've always known otherwise . I don't know what type of switch you're using; but there are plenty of 40 KM 1G SFP's for EX switches referenced here . Here are some samples :
EX-SFP-GE40KT13R15
EX-SFP-GE40KT15R13
EX-SFP-1GE-LX40K
And here are some that support more than 70 KM ( there are even those that support up to 80 KM ) :
EX-SFP-1GE-LH
EX-SFP-GE80KCW1470
EX-SFP-GE80KCW1490
And they all support virtual chassis. If there is some limitation I'm not aware of that restricts your use of these SFPs in your setup then you should check finisar for compatible SFPs as an alternative.