In my mind seymour does have this anger stewing inside him. He was set up from the start to be failed by the system, stuck in skid row, with an adoptive guardian who used him basically as free labor, he dropped out of grade school, used to being a dissapointment from said adoptive guardian, and realizing hes too much of a wimp to help audrey with her abusive boyfriend. Audrey ii to me at least helped encourage those thoughts and impulsive decisions, feeding into his fantasies of success. as soon as he helps twoey, he can live the life hes always dreamed of. hes not squeamish at the sight of blood, we can tell already, but i think as soon as the moral weight of killing someone hits him hed have a panic attack and audrey ii would have to coax him through it. Hes in too deep now. He has to finish the job. After feeding audrey ii hed run to throw up, her laughs echo in his mind as he empties his guts. He stays up all night due to the adrenaline and anxiety of if the shop was cleaned thoroughly enough so none of the customers notice the red spots on the linoleum. The pay off lead him to stay in the cycle of killing, he got the girl of his dreams and the attention of everyone in America he cant stop now!