1. Where is the money ?
Money repaid goes to the MFI, then to KIVA, where it will earn income for KIVA.org until the loan is paid in full.
2. Who is making use of that money and for what purpose ?
KIVA.org - operating expenses
3. If that money was back in my account, I could re-loan it.
there has been a little discussion of this happening, but nothing of recent.
4. Kiva shows that it has made loans of nearly $22 million. I don't know how much is typically outstanding at any one time but this could still conceivably be a huge amount of cash.
If you click on an MFI (field partners) page, you can open up a lot of the stats, you'd be surprised, I think this answer sits there.
5. This is most unconventional. ( I realize that Kiva is also unconventional.)
good point!
6. I assume that part of the funds are with the various partners as the links between lender and borrower are a little longer than our domestic banking system.
I believe, roughly 'monthly', to keep cost down, wire transfers happen each month - I think they use some 'net' calculation for which way the money flows.
Wow, that was fun....
and Great questions for a school group to have fun with!disclaimer... I'm probably wrong on all these answers, but close!!!!

And, a big big welcome to KIVAFriends!!!!