Your questions are all very interesting. I think there are some ways to defend from the Misfortune Spell, but I need to check them point-wise:
Can you use fate and then the Cloverfield to choose a new result? If you do this, you actually do not reroll the die. You actually do not roll it.
I don't think you need to use fate. Fate implies a chance of re-rolling, no matter if you use the Lucky Charm and decide which result you score.
I think you can use the Lucky Charm to cancel the effect of Misfortune and choose the result anyway, since you're not re-rolling the die. I think also the Marked for Glory Spell can work this way. For this it's better to ask for official confirmation.
Can you use fate and then Twist of Fate (Spell)?
I'm afraid this is not allowed, since you need to spend Fate to cast Twist of Fate. If you spend Fate you're actually starting a re-roll process and I think this is what Misfortune is meant to prevent (no matter if you actually re-roll or not).
Can you use Moon Charm (Reward): Keep this card. You may discard this card after rolling a die to change the die result into a 6 result. ?
I think this works perfectly. It changes the result of the die without actual re-rolling.
Misfortune is a gruesome Spell, but it's not overpowered. Such Spells are a great danger for leading Characters and can result in sudden death, which is rather impossible by normal means. When people will get used to the presence of such Spells, I think they will become extra careful in their lingering on the board while they're more than Crown-ready. I like Misfortune for this reason, finally there's a Spell that can put a strong Character in real danger. In the Inner Region, the Misfortune Spell cannot hurt you, except if combined with other Spells (Vindication, Random).
By the way, if you have Misfortune you can keep it and use it in the Mines or Crypt. In some cases a 1 result is a lucky one...it's also an interesting result for the Judgement day ending, if you have too many chances to lose with a normal roll.