It’s been a while since I’ve made this cake (I’ve made it twice), but I remember my layers being about an inch thick as well, so this sounds about right to me. I also found my cake a bit crumbly, but I think that’s okay. In fact, I also remember that within any given layer, once baked the rings did not fuse together and if I wasn’t careful it could easily fall apart when handling the individual layers (luckily that didn’t happen). I think it’s a good thing if your cake is somewhat crumbly. As long as it’s not too dry or too moist, then crumbly means you have a good cake crumb because if it’s too dry then it tastes funny and if it’s too moist then it’s too dense and either way it doesn’t taste all that great. I don’t know if you level your cakes before stacking the layers, but if you do (which it’s NOT necessary), then you can taste the top that has been removed and you’ll know if it tastes good or not which is why I like to level my layers (plus, it makes them easier to stack for assembling). Good luck with your show and tell and I hope it all works out for you.