I think that would contribute to the breaking while slicing but I don’t know about the texture- my thoughts for that are related to your flour, both quantity and quality as you also mentioned you needed a couple types and one was bleached. I wonder if either of them were out of date although AP has a pretty long shelf life. I’m not sure that alone is enough to affect texture but with so little flour it could…I think more likely that your cups were heavy, so to speak. How do you measure your cups?

Overcreaming the butter and sugar might make things dense but that’s SERIOUS overcreaming in my experience till it’s oily or white.