For example, the exp share is on, and the Pokémon fighting gets 2,000 exp, and the team gets 1,000 exp divided among them. If the exp share is off, will the Pokémon fighting get the full 3,000 exp, or will it still get 2,000 exp? I've tried looking at websites trying to find the answer, but nowhere has been specific. Please answer this asap.
As of Generation 6, the Exp Share doesn't affect the amount of experience received by Pokémon who participated in the battle - they receive the same amount of experience either way. All Pokémon who participate in the battle receive the "full" amount of experience, and if the Exp Share is turned on, all other Pokémon in your party receive half that amount.
You might want to turn off the Exp Share are when you want to give your Pokémon particular EV spreads, or to increase the challenge of the game, but it has no detrimental effect to the amount of experience you gain.