For some students’ federal college loans, Uncle Sam might be ready to forgive and forget. The Student Loan Forgiveness Act of 2012 aims to erase the federal student loan debt of academia’s most dutiful borrowers — those who have already paid 10 percent of their discretionary income servicing their arrears over 10 years — and cap interest rates at 3.4 percent. Introduced last month, the proposed amnesty applies to debts up to $45,520, or about a year’s tuition at a top-dollar school.