You see, according to some theories, Anakin’s turn to the dark side could have been prevented.
In the scene where Qui-Gon is battling with Maul, it’s theorized that Qui-Gon’s meditation was not just to restore energy. Qui-Gon, being able to see into the future may have been able to see his own death; and while he could have changed it through the force, he chose not to, as he believed strongly in the will of the force; meaning that if it’s bound to happen, it shall be let to happen. This mindset is unlike the mindset of the Jedi Council in the latter years of the Republic; where the Jedi changed the will of the force to their advantage.
Now, if Qui-Gon had changed the force to his favor and lived, he would’ve been there to train Anakin; which would have significantly lowered the chance of him turning to the Dark Side. But that would mean that (providing Anakin had children in this future), Luke and Leia would have become vulnerable to turning into the Dark Side (as they would most likely be trained by Anakin and not Qui-Gon or Yoda). This would be an ultimately bigger threat, as Luke and Leia each are stronger in the ways of the force than their father, and there is two of them.
If Sidious had pursued Luke and Leia to the dark side, they would be able to deal far greater damage than Anakin/Vader did and unless one of them had children, there would be noone capable of stopping them.
Now to answer your second question, well without Padmé, no there wouldn’t be a chance to destroy the Sith, but without her, there would be no sith. Remember, the key factor that Sidious used to persuade Anakin to the dark side was saving Padmé. If there was no Padmé, Anakin was far less likely to become a sith.
