The one with Blaine dating Rachel im pretty sure is called "One More Night" (or another maroon 5 song, but I'm pretty sure it's that one) and there's a trailer for it on YouTube
It was originally written by beautifulwhatsyourhurry, but never completed.
One More Night by beautifulwhatsyourhurry
Kurt Hummel is hopelessly in love with Blaine Anderson. The problem? Blaine is taken. And popular. And so very straight…or maybe not.