I mean even ignoring the mod posts, Jin Woo to me just seems like the perfect third party. As the show goes on and as his powers developed, he seemed to me as if he was growing more and more of a sociopath. Seems to not really connect to anyone and allies only with people who bring direct value to himself. Never really makes an attempt to get with Lee Johee who makes it obvious she wants to date him, even when he was an E rank. He cares about his sister and his mom, and Yoo Jinhoo to an extent but that's about it. He seems to lose more and more of his personality as the show progresses, and ultimately I get the vibe that he's taking on dungeons and monsters purely for the sake of getting more powerful. Like if I was designing this game it would take a lot of weird reasoning to not make this character third party.
I have a hard time believing that Sung Jin-woo is a full-on third party. At worst, I'd say it's likely they have options for achieving their wincon, though those still almost certainly overlap with town. I agree that he changes over the course of the series and even with the sociopath label, but as Mestari already mentioned, he's instrumental for making this raid on Jeju Island successful in the end.
Maybe. I would be suspect of player characters more so because I feel like they are easier to fake claim, since the mod said they were confirmed to exist. But both thoth and alyssa have claimed actual characters, so yeah theres something to mafia having fake claims for sure assuming alyssa also flips scum. There is a decent chance they used all of them by this point, 4 fake claims seems like a lot. I can see 2 being realistic. I also theorized that the player characters were added in after mikal balanced this. He was initially telling me he wanted 13 players, and we ended up getting another 4 after that. Makes me wonder if the 4 added after were all just player characters.
I would not be surprised if the remaining scum claimed themselves as their characters, partially because they might lack for additional fake claims, and partially because claiming characters from the show puts them in a similar position to Thoth and Alyssa.