Hello! Thank you for trying my recipe, and I'm sorry you are having problems - if the batter looked curdled then your butter was too warm. It needs to be 68 degrees or slightly colder.
Some words of love: if you don't make the recipe as written, you can't get frustrated that it does not turn out as great as people say it is. I'm sorry, but that is the harsh trust about baking scratch recipes. You need to make the recipe exactly as written, at least for the first time, and make it to the letter before proclaiming it a failure to you. Think about your scientific method here: you could have spent under $5 just buying a few readily-available ingredients, made the recipe exactly as written and had a success the first time out. Instead you decided not to spent the extra few dollars initially in favor of trying how many different recipes? Not following them to the letter, burned thru countless hours and money in ingredients - and are now completely frustrated because they didn't work. You see?
I go to really great lengths to explain why I use the ingredients I use, and I let you know when you can use substitutes and when you can't. The recipe on my blog is written using cake flour, and I say on the blog post that you should only use cake flour. No substitutions.
As for buttermilk, I also go into a lengthy explanation on why we use buttermilk. If you don't have buttermilk use whole milk. I admit, I need to write an update to that post addressing the insanity of people doing the vinegar+milk thing. IT DOES NOT WORK. Vinegar does not produce cultures. Cultures are emulsifiers. Emulsifiers are the good bits that we want in the cake. What vinegar does do is kill your the leavening, kills the remaining emulsifiers in the sour cream, and jacks up the pH. I know the internet says this works, but I assure you, it does not work as a replacement for buttermilk in a cake recipe that relies on the cultures in buttermilk as an emulsifying agent.
It's also possible you are looking for a unicorn. Scratch cakes are not "moist". "Moist" is a BS term used by the cake mix industry to explain the mouthfeel of the antifreeze they put in cake mix that helps prevent the clueless home cook from baking their frankencake into a brick. A good scratch cake has a soft, delicate mouthfeel that isn't dry, but it isn't "moist" and never will be.
You need to let scratch cakes mature from the oven. It's strengthens when your hot cake is popped straight the freezer for a few hours to a few days (wrapped in plastic). If you leave your scratch cake out of the pan on a cooling rack for hours (like you can with a box cake) it will totally dry your cake out.
There are lots of recipes out there - my final words of wisdom for you is to pick one that uses the ingredients you want to work with.
Best of luck,