As the title says, I have one particular player that has a digital file version of Curse of Strahd and is hellbent on cheating. They have done just about everything from faking dice rolls, using weighted dice, reading ahead, reading the monster out loud to the party in the monster manual, etc. I can't even kick them from the party because we play in a school club and can only kick people if they are breaking the rules. I have tried changing the stat blocks of the monsters, removing balance from his GP (basically fining him), and giving him hard solo encounters, but nothing seems to be working, what should I do?
Given this is a school club activity, you most likely have a staff advisor for your club. You should talk to your club advisor about this problem player, specifically about how they're ruining the fun for other players by spoiling the adventure, removing (much of) the challenge from encounters, and plain old cheating (using loaded dice or faking rolls). You'll want to do this in private (away , at least at first; this is the kind of thing that's best done that way, so in case you're incorrect about the situation, you don't generate hard feelings.
The staff advisor is likely the one person who actually has the authority to deal with this kind of behavior -- including, if it comes to it, removing the problem player from the club. They might, however, assist instead by counseling your on how to deal with this yourself, without involving an authority figure.
Don't try to use in-game means to fix it.
Trying to use the game itself to deal with the problem player (hereafter TPP) is going to run into several problems, foremost among which that TPP is playing a different game than you are. You're (presumably) trying to run Curse of Strahd to give your players a good, if challenging, time; TPP is trying to "beat" everyone, including you.
If you start trying to "beat" them in response:
- you engage them on their own terms, lending it a legitimacy you definitely do not want it to have,
- you buy into the arms race of cheating vs penalties, which tends to reinforce and escalate the whole matter instead of solving it,
- and you run the risk of dragging the rest of the table, who are still trying to play your game, into having to play TPP's. The party is losing GP because he gets fined, his overpowered solo encounters can easily spill over and take a non-cheating PC out, etc.
Talk to your player.
Don't frame it as 'you need to leave'. Explain to them what their tactics are doing to the game, and how they're getting in the way of anyone - especially you - having fun, which is what you came here for in the first place. Enlist the other players or pass along their concerns if you need to, to reinforce that the behavior is degrading the play for everyone.
Ask them why they feel the need to do it, and be ready for these answers:
- Curse of Strahd is known for being a difficult and punishing module, even if it's not the worst of them. TPP may answer that they cheat specifically because the module "cheats" by being so difficult. Explain that overcoming the difficulty is not the point of the game - or, if they insist it is, offer to run a different module.
- They may explain that they're being singled out by your countermeasures and don't have a choice but to cheat. They're not entirely wrong. Explain to them that the singling out is because of the cheating, not the other way around. Acknowledge the vicious cycle and offer to start again with a new understanding.
If they don't listen, find someone who will.
If TPP absolutely will not listen to you, talk to the club organizer. Explain to them everything you've told TPP. Go over the rules with them; the knock-on effects of the cheating will almost surely break one of them. They will be in a position where they can make the call that they won't let you make. And be receptive to what they tell you; they might, for example, have an insight or perspective on the situation that you don't.
If they don't listen, then stop running the game, at least for TPP. Not running (or playing in) a game is preferable to one that makes you miserable, and if you've followed this, you've already made your case to both TPP and the club why their behavior is problematic and why you can't go on like this.
If the club still opposes this exclusion, the club is showing you who and what they value, and it isn't you. That's not a club you want to be part of. Find one that values you, and don't look back.
Talk to the player
If there is a problem, you should talk to whoever you think is causing the problem, without being accusatory. You should talk to them alone to not make them feel pointed out in front of everyone.
You should be nice but be clear on the problem. Explain
- how cheating makes you uncomfortable
- that D&D still has rules, just like a board game or game of sports even if it is not one of those.
- that cheating in D&D should not be necessary to enjoy the game or succeed.
The latter point is especially important. Tell them that if the player finds cheating necessary because they have a problem with the game, that you would be happy to have them tell you about that problem to find another solution.
Talk to whoever said you could not remove the player - or leave
Now, it is almost always worth it to talk to other people personally and nicely before taking extreme measures.
If talking to the player does not help, you should talk to the person(s) making the rules (such as the rule about when you can remove a player). Describe the player and ask them for advice.
If this conversation is also unproductive, i.e. you are given neither permission to remove the player from the group nor advice on how to resolve the problem otherwise, you should really think about whether this is the place to run games. Generally, though, people running school clubs should be both competent and willing to resolve problems in groups (rpg or others).