1. if anyone was effected by a negative role that could be mafia aligned, should they claim it? yes/no/why
It's case by case, but I'd say yes in the majority of cases. Why is because it can't do any harm. The mafia knows who attacked who already, so it's not giving them any information. For the village, it helps us to know what role is in the game and to check lies in future cycles when we need too. There are about 1000 different roles in the OP and I don't remember half of them, but I'm sure that one of them was something like a watcher for the village who could give us a mafia lynch at somepoint.
Not speaking up now might not mean speaking up at all. And unless there is an explicit reason why you shouldn't claim you were targeted, I'd say you'd need to. The mafia can lie and make up an action and say that they were hit by something, but if they do in later rounds they'll be caught in the lie.
2. assume you're controlling night kills and night starts now. Who is your night kill? why?
I'm assuming that by night kills, you mean anti-village and not a vig.
The act of choosing a target is delicate. Obviously, I'd want to go for the big guns and get a big name off the board. Someone like DLE who has the mafia experience to lead the village to a quick victory and catch me or my team if I have a team, quickly. But going for him is risking losing a kill because of his experience and the clout around his name, he'll have the highest likelihood of being protected. The player who is inactive or inexperienced is the one least likely to be blocked, but at the same time they're low reward. Yeah, they might be a good role, but if they're inactive or inexperienced they won't use it well to begin with and will probably get themselves lynched. They're also the ones most likely to be fooled and manipulated later on in the game.
So, my target would probably be someone in the middle. Someone like Cancerous or Ullar who have mafia experience but who won't probably be protected. Seems like the best risk/reward ratio.