Sigh. Well, it's possible this boot is legitimate, but it smells weird. Here are reasons Danny might have gotten voted out:
I agree with your reasons on both sides, but I would add -- was the performance memorable? People who love Danny obviously enjoyed the performance, but did the casual voter?

I think something like the Jailhouse Rock performance would have gotten him into the top twelve.

The same with Asia'h, she gave a safe, useless performance. So did a lot of the other girls, but they either had strong pre-existing fanbases, a history of good performances, or in Kristy's case, tapped into the country market.