Weakness
This is perfect. It makes so much sense for Snape not to give to Draco what he is looking for. First, there is politics, and second, there is his love for Lilly.
The Malfoy's downfall being caused by Draco's failure as the last straw - I loved it.
I felt so sorry for Draco, and I was very happy that the story ended on a somewhat positive note, with Draco being able to feel a bit of freedom. I loved the Hufflepuff-ish reaction of Andrew, who didn't take revenge on Draco.
And last but not least I truly enjoyed your description of Legilimency and Occlumency. I love fics that explore the "mechanics" of magic, and you came up with an excellent imagery of how to read another person's mind. Walls build of layers and layers of webs - *happy sigh*
Thank you so much for this wonderful and many-layered story!