New questions emerged Monday about the FDNY’s denial of 9/11-related disability benefits to a retired firefighter who labored at Ground Zero and then suffered severe psychiatric illness before dying in a mental hospital. Joe Battista spent months at the World Trade Center site after the 9/11 attacks and developed serious health issues, and severe depression and post-traumatic stress disorder that led to repeated hospitalizations. But the FDNY repeatedly denied him World Trade Center disability benefits. He choked to death on food at a Florida mental hospital on April 5. He was 63. An FDNY official suggested in Monday’s exclusive Daily News report that the department repeatedly denied the benefits because his condition had not been properly linked to 9/11.