Nope. They can't remotely share their chakra in their seal. The only way they're breaking the genjutsu is with katsuya and even then it's still just katsuya breaking it and not them.
This is a good question. I don't see why not. They only need to stream chakra into the victim to release the genjutsu right? Maybe this will be how Sakura surpasses Tsunade or does something original with her powers for once.