1) While a positive balance on a bank account is considered a loan since the bank may use the money for whatever purpose they choose, according to most opinions one may still withdraw the money from a Jewish-owned bank after Shmitta even if no pruzbol was made. The reasons are that the bank is a corporation not an individual and many opinions hold that a corporation does not need to forgive loans nor are loans made to a corporation forgiven. Additionally, since the bank is closed when Rosh HaShana begins it is considered by many to be a loan whose time for payment has not yet arrived. However, one should still preferably make a pruzbol on a bank deposit to cover the other opinions.
2) The Kol Sofer and Mishnas Yosef write that one should accept the loan in order that the borrower fulfill his ruach chachomim nocha mimenu, I didn't see any discussion why his intention is not sufficient. Reb Shlomo Zalman Aurbach zatzal adds that even after shmitta cancels the obligation to repay the loan the loan itself still remains and it is not completely a gift to return the loan. Therefore there is no concept of sone matanos yichye to refuse to accept the gift/repayment.