. . . Person A's $80 is not lent out "multiple times" because the bank that is not a central bank can't print dollars. The $80 leaves the bank in the form of cash in a loan, therefore it is lent once. Cash is king and cash is final. I don't understand where you think this $80 can be lent out multiple times without ever being paid back. You are wrong. Very wrong.
You are mistaken on this point as well.
Here is a scenario:
A total of $1000 in actual physical currency exists...
Alfred deposits this $1000 into an on demand checking account at a bank.
(Bank deposits $1000, Bank loans $0, Reserve on hand $1000, Reserve 100%)
Betty receives a loan from the bank of $800.
(Bank deposits $1000, Bank loans $800, Reserve on hand $200, Reserve 20%)
Betty uses the $800 to purchase something from Charlie
Charlie deposits the $800 that he just received from Betty into his own checking account.
(Bank deposits $1800, Bank loans $800, Reserve on hand $1000, Reserve 55%)
Denise receives a loan from the bank of $640. (re-loaning out the same money that was already loaned out to Betty)
(Bank deposits $1800, Bank loans $1440, Reserve on hand $360, Reserve 20%)
Denise uses the $640 to purchase something from Elliot
Elliot deposits the $640 that he just received from Denise into his own checking account.
(Bank deposits $2440, Bank loans $1440, Reserve on hand $1000, Reserve 41%)
Francine receives a loan from the bank of $512. (re-loaning out the same money that was already loaned out to Betty and Denise)
(Bank deposits $2440, Bank loans $1952, Reserve on hand $488, Reserve 20%)
Francine uses the $512 to purchase something from George
George deposits the $512 that he just received from Francine into his own checking account.
(Bank deposits $2952, Bank loans $1952, Reserve on hand $1000, Reserve 34%)
Hanna receives a loan from the bank of $409. (re-loaning out the same money that was already loaned out to Betty, Denise, and Francine)
(Bank deposits $2952, Bank loans $2361, Reserve on hand $591, Reserve 20%)
Hanna uses the $409 to purchase something from Ivan
Ivan deposits the $409 that he just received from Francine into his own checking account.
(Bank deposits $3361, Bank loans $2361, Reserve on hand $1000, Reserve 30%)
At this point we already have $3361 in deposits from that single $1000. Alfred, Charlie, Elliot, George, and Ivan all believe that they are the true owners of this money since they each held the physical cash in their hand and then deposited it into their own checking account. Where did the extra $2361 come from? Meanwhile the bank has re-loaned out the same money over and over without a single cent of it having been repaid yet.
This process can continue over and over, expanding the money supply until there is $5000 in deposits, since the maximum the bank can ever have in reserve is the full $1000 of physical cash in existence. This would result in $5000 in deposits, $4000 in outstanding loans waiting on repayment, and $1000 in reserves. Notice that at this point the "PAYBACK AMOUNT OF THE LOANS PLUS THE RESERVES", as you put it, would be $5000, but there is not $5000 of "real money" as you state.
Now, what happens if Alfred decides he has found a new bank that he likes better? He withdraws his full $1000 from this bank and deposits it into a checking account at the other bank. Later that same day Charlie tries to withdraw $10 from his account, but the bank no longer has any reserves because Charlie unexpectedly left with all of it. Where does the bank get the money from to allow Charlie to withdraw his money?
Notice, at this point the bank fails, and there isn't a single person who defaulted on their loan.