Thanks for the input! Though it'd be nice to get additional language and research preparation with the Stanford MA to hit the ground running in a PhD program later on, perhaps it's crazy to let go of Columbia now since its such a great program and right there in front of me.
anoveldave, I was informed by an email on the 21st that led me to the application website, where it showed a status update link leading to the acceptance letter once I got to the page with the references, uploads, etc. Shortly thereafter my POI sent me an email about the good news. Apparently some extra funds were freed up recently, allowing them to take me on, which is why it took so long. Maybe it's the same case for you, so good luck!