Excess ingredients? Cooked shell cracked. Slimy after 24 hours.

No, I don't think there are any excessive amounts of any of the ingredients called for in the recipe. Whether you call it a meringue pie crust, a pavlova, or just a plain old hard meringue- it's all the same thing. You have whipped egg whites to hold about as much air as an egg white can, and the aim is to come up with a stable structure that can hold it for a while. Oh, and it has to be edible, fairly easily, and taste good. Egg white on it's own can't really do that. If you didn't have the cornstarch, both plain and in the confectioner's sugar, you really wouldn't have anything except a pile of dried up egg white. You may have had cracking for a few reasons. You may have not piped the mixture quite closely enough or thick enough to stay stuck together as it dried. You may also have had an oven temperature just a tad bit higher than it needed to be. And yes, it does need to start off fairly substantially thick, especially where bottom and sides meet. Gravity, and all that. They are also not what you would call long lasting creations either. All that sugar means it remains a water magnet, and as time goes on, it attracts more and more. In the 12 hour chill, it would have absorbed enough from the filling to become rather marshmallowy, with just enough body to slice and enjoy without shattering apart. After 24 hours, well, yeah. It starts to dissolve, and get slimy. There isn't a darn thing you can do to stop that either. You can make the meringue part ahead of time, if you keep it in an airtight container. You can make the various fillings up ahead of time, too. But those two things can't meet for more than a few hours, up to about 12, without ugly things happening. Sorry, it wasn't you. It wasn't a problem with your recipes. It was time, moisture, and just the way egg whites and sugar work. Still, bet the filling was scrumptious! I mean, CHOCOLATE!