Great questions, some stuff I hadn't considered yet, I'll try to give some detailed answers here.
1. They would find out the role of a Janitored kill, yes. I would think that if they used it on someone who was not Janitor killed, then they would receive just the faction of the killer as their info. If they did use it on a Janitor killed player, they would receive the Role PM. They could possibly receive both the Role PM and the faction of the killer on a Janitor killed person too, but if that seems OP then it could just be the role.
2. The Mafia does not receive the role from the Janitor killed player.
3. Yes. I had been considering the idea of keeping it so that Mafia would not receive the results no matter what, but I think I would rather keep it fully randomized.
4. This is something I had forgot about. Yes, I would probably want the Mafia team to get fake roles to claim since it is a Role Madness game and I'm pretty sure the others I've seen so far also had fake claims for the Mafia. We had fake claims in Conspiracy, and from what I remember they were like passive roles or hard to prove/disprove ones, I definitely remember that Medium was one haha. So yeah, I would need to probably figure out some role claims for them to have which I can add to the spreadsheet.
5. This is something I hadn't considered. I think I would rather keep it to one shot of each for the JoaT, so once they use the Janitor shot, they can't use another one, they would only have the one Ninja shot remaining.
6. Something else I hadn't fully considered. I know in Conspiracy I was refunded my 1 shot when I was blocked, and that made sense because it would otherwise have taken away my whole role from me without anything I could have personally done about it. I would say yes, but on the other hand I have pretty much everyone sitting at 2 shots right now for their abilities, so maybe only the 1-shots would get them refunded? I'll think on this some more.
7. The Cop's check would not be sent if they were killed at night.
8. Town could be a bit OP currently, yeah. I had actually been considering making the Cop a 1-shot instead, but keeping the Doc and Watcher at 2. I had the Doctor at 2 shots since there will be the 2 night kills going while the SK is around. There is also the Hider though, and the SK needs to dodge the Godfather's NK immunity as well. I think I would still leave the Watcher at 2-shot, but I could see maybe bringing down the Doc and Cop to 1-shots just to bring down the Town's power a bit there, yeah.
9. 1 Town, 1 Mafia, 1 SK ending. Huh, I'm just going to think out loud here for a bit on this one:
I suppose it's either the Mafia or the SK that gets the win there? Town gets shot by Mafia (natural enemies, after all) and then the SK shoots the Mafia and wins? But what if it was the Godfather? He's immune to the kills, does he override the SK and win instead due to that? I guess I could also let the SK win as a Neutral Survivor, that would just mean that situation would be LyLo instead, right? So if Mafia gets lynched, SK wins with Town, if Town gets lynched, SK wins with Mafia, if SK gets lynched, Mafia wins? Is that how that would work then? That might be best just to make it easy, but then I feel like the SK could just never kill and go about trying to get that Win Con instead, right? So maybe that isn't the best idea. Unless I make it so they have to submit a kill each night, that's a possibility I suppose to avoid that situation, right?
Ok, so yeah, that last one is something that hurts my mind a bit to think about lol. Let me know if any of that rambling above has any sense in it. Is there like a normal way for that to play out or is it just kind of a Gamerunner's discretion thing?