There are three things you need to know before going to your first bare-knuckle fighting event. There will be a lot of blood. There will be a lot of nicknames. There will not be a lot of nuance. “My goal is to go out there and punch him as hard as I can without breaking my hands,” said Jake Heffernan, a bulky, five-foot-nine, tattooed 35-year-old father of two from Houston who, sitting in his kitchen, looked like a slightly larger version of Conor McGregor, the brash, bearded Irishman who held two championship belts in the Ultimate Fighting Championship simultaneously. Heffernan spoke calmly but forcefully. “I want to be ready for the dogfight: to go every single round and be bloody at the end.” Heffernan’s career had been…