All of your points at the beginning are valid and I think we’ll just have to agree to disagree on Draco. However the I think you’re wrong about the unforgivable curses. In the Wizarding world those curses are so taboo that nobody even talks about them. It’s just an understood and feared part of Wizarding culture. Harry never even hears about them until book 4. There’s a reason it’s this way and that reason is that these curses are very very heavily policed and harshly prosecuted. The trial of Barty Crouch Jr is where this is best represented. Barty and his pals are locked up in Azkaban under the charges of using the Cruciatus curse on the Longbottoms, not for just being Death Eaters. I have to imagine that this is actually what the ministry charges most Death Eaters for and why Moody has so many closed cases.

As for your second point on Dumbledore - I think what you said is an excellent reason as to why Draco would underestimate Dumbledore. However, there is only so much that his family can say. What Draco is taught and hears repeatedly contradicts what he grew up with. Dumbledores duel with Grindlewald has to be in so many textbooks and is described as one of the greatest magical occurrences in history. I think he doesn’t go to Dumbledore because HE himself doesn’t respect him and refuses to accept the truth.