1. I think that Nightmare Moon will handle those. And if she doesn't, I'll destroy the Tree of Harmony by draining all the love and friendship from it. Then, the Elements will be powerless. I also have to get rid of the Box of Friendship/Rainbow Power, by, maybe crushing it whilst the size of a dragon will work? Then, they'll pretty much be powerless.
2. The rest of my fellow Changelings will be free to roam and do whatever they please in Equestria. Unless, I forbid it.
3. Royal Canterlot Voice: WE THINK OUR PLAN WILL UNFOLD SMOOTHLY!! DOST THOU HAVE THY PROBLEM!!??