The old adage, "Don't get hit" is the only actual advice I can think of against the IC. Though in this case "Don't get grabbed" is more suitable. But really, there's not much you can do except practice against a very avid IC player to understand their mannerisms.
But onward to actually useful advice, you had it on the second stock. If the IC player is going to exclusively use his/her/their trump card, fight fire with fire with yours. Which in Pit's case is the ledge game. Though the IC still have the advantage you can keep out of their arm's reach and maybe get them off the edge if they fall into a punishable pattern.
Another thing to learn is Smash DI. Insanely hard to use in the proper situations, but when playing with Pit on the edge it can help a lot. Many of the meteors that you can get nailed by including the IC Fair can be Smash DIed into the stage wall and teched. Though this is very difficult to get down consistently. So much so that you'll rarely even see it in high level play.