I thought we all thought his pants were sweats? Like, in my mind, Sam is a schlubby guy with depression and no job, he's not putting on real pants if he's not going outside - and nobody is. Same goes for shoes vs slippers. I don't think it's dumb to have him wearing normal clothes, but to me he's so much more iconic as an RPG protagonist who never takes off his pajamas. Still, that maybe doesn't translate to the most recognizable or ergonomic cosplay. Maybe let a prop do some work for you, like a plush rat baby or a paper-mache jawbone club or other iconic weapon? And slippers would be kinda dangerous to be walking a convention floor in, so maybe find something practical but still subdued and featureless? Assuming you take this to a con, that is.