Yeah. Adding mental tampering on top of mental tampering is not a really straightforward question.
What a lovely incentive system the Valar have set up. 'Hey, you know that evil guy who could maybe tamper with minds, let's make sure seeking help with disentangling that is really unappealing'.
Incentives are such a useful way to think I barely know how I'd model anybody without having them in mind.
The best way to model the Valar is as having - actions that are in character for them and actions that are out of character for them, and no stakes will get them to take an out of character action, or change what sorts of actions are in character, and they all have different characters and for some of them things like 'preferring to minimize loss of life' are in character but not all of them.
If what's in character for him is 'torture people for fun' and 'orchestrate the destruction of everything he touches' then he cannot be deterred from that. If what's in character for him is something more like 'experiment and discover things' or 'break things that others make' then maybe he can be deterred from manifestations of that which involve torturing people and destroying things, unless 'don't respond to deterrence' is a trait of his, like it is one of Manwë's.
No one; why bother? Manwë's the King of the Valar, and has been explained variously as 'incapable of comprehending evil' - that is, committed to interpreting everyone as doing badly at fulfilling Eru's will - or as 'incapable of planning around other peoples' reactions to his actions being anything other than how they'd react were they maximally virtuous'.
These sound like they will impair his effectiveness as a king. Like. A lot.
"That'd be interesting. Not a big moneymaker though, restaurants have really narrow profit margins and I don't think you could completely change that by getting all your ingredients free."
"There are places that do that but they're usually charitable or eccentric. I guess you could fit 'eccentric', albeit differently than a church or someone trying to advocate that everybody eat lots of potatoes because they really like potatoes would be."