Your current moves are completely fine for ingame
Sky attack, while powerful, has a drawback which is a waiting turn, during the waiting turn you are prone to attacks. While Fly also has a waiting turn, you can't be damaged by attacks for that turn. And it is generally better in game as you can use it to fly to different locations. After a D-Dance boost, Fly would easily be capable of taking out the same Pokemon as Sky Attack with none of the draw backs.
Perish Song is only good as a finishing move or to force switches in competitive, which you aren't doing. By the time those 3 turns are up, you have probbaly either KO'd the oppoenent or got wiped out, if it's late game at least. It's a waste of a moveslot with little practical use.
So, you're fine as you are. Set is good to use.