Continuity mistake: When Frank Castle walks up to Murdock, the chains are wrapped around his torso, two over his chest and three over his abdomen, but when the shot cuts, it's one over his chest and four over his abdomen. (00:17:40)
Continuity mistake: When the Punisher knocks out Daredevil he wakes up with a gun taped to his right hand. When the Punisher says that Daredevil has to shoot him, Dardevil struggles to escape from his chains and we get a shot from his right side, where the gun is no longer there. In a later scene it returns. (00:32:05 - 00:34:55)
Chosen answer: After some research, I can say that no, Cass is not a character of Marvel, nor is he present in the Netflix show. As far as I can tell, it's either a real person, or a random name chosen for the coffin, most likely the former. In another season of Daredevil, the show utilized a real cemetery displaying real names in the tombstones.