If I give an exp.share to a Pokemon and in battle I send out a level 100 Pokemon and I win, would ALL the exp go the Pokemon with the exp.share?
It will still give it 1/2 of the experience, but in that case, it's better to send the EXP. Share equipped Pokemon out first, then swap it with the lv.100 At that point, the equipped Pokemon will get 3/4 of the experience.
Im possitive that it gives it half the exp gained from the battle, at the Pokemon (The one holding the exp share's) rate of exp.
The Pokemon that was first with experience share doesn't get all of it because it did nothing and even though the one you sent was 100, still will put down experience for the other(s).