The biggest issue with Dumbledore is that he is acting arbitrarily. We are getting his actions essentially through the same lens as Harry is. We have it only on your word (as both narrator and Dumbledore) that Dumbledore means well for Harry. He is so paralyzed with fear in this incarnation that he is doing nothing to engender respect or sympathy - and to the extent that he is doing anything, he is preventing Harry from seeing Draco. I could easily sympathize with this, but it comes across more as an accidental intended benefit than an intentional intended benefit. You have made Harry's starvation and abuse sufficiently obvious from Harry's point of view - despite the fact it took Snape ripping it from Harry's brain and Draco being told by Snape - that Dumbledore appears at fault for not noticing (as does Snape, and even, to a lesser extent, Draco, for being so easily put off by Harry's words). He is not coming across as evil per se - simply as completely misguided and utterly incompetent. As this is a fairly significant deviation from his character in the books, Dumbledore does come across a little bit out of character - and a lot more rage-inspiring.

Though in my opinion Harry and Snape win the infuriating contest with their dueling martyr complexes.

I absolutely love this story!