You might want to think twice about three mega stones on a team, wherein you can only mega evolve once per battle. If you want to keep your pokemon, let me suggest movesets:
It's fine, but consider Dragon Claw instead of Dragon Rush. If you can, try to get the Rough Skin hidden ability.
Earthquake would definitely help in that moveset. Also consider Brave Bird.
Replace Hydro Pump with Scald so you can halve your opponent's attack with a burn. Since you'd have a burn already, replace Toxic with Rapid Spin.
Don't waste your time on Future Sight. Use Grass Knot or Calm Mind. I suggest Psyshock over Psychic in case you encounter Blisseys. Flamethrower would work better with the higher accuracy. I'm not sure about Light Screen, so keep it if you want to. Just hold leftovers if you're using Light Screen.
Not bad, but I suggest use Black Sludge instead for the item.
Don't mind my comment earlier, don't use flying gem. Don't use acrobatics. Give it some leftovers and then replace Acrobatics with Swords Dance/Bulk Up. Replace Flame Charge with Flare Blitz since you won't need speed. Use Gale Wings as your ability. Use Roost instead of Fly.