A Staten Island power couple made up of the district attorney and a state Supreme Court judge are under scrutiny for “double dipping” by taking in hefty taxpayer-funded salaries and pensions. Both DA Michael McMahon and Judge Judith McMahon are getting paid six-figure salaries while also collecting government pensions that are likely more than $100,000, The Post has learned. DA McMahon “retired” from government service in December — while remaining the borough’s chief prosecutor — and now collects a pension that is likely upwards of $130,000. McMahon, 66, a former legislative staffer, councilman and congressman before becoming district attorney in...