Looking at your stats I would have thought that noise is the problem?
Noise margin on good line: 8.5 dB
Bad line: Noise Margin 6.1 db
I have a noise of about 6, and my speed synched at 5Mbps by the end of the test.
I did some investigation, and swapping out the old microfilter and putting the new one in, made a huge difference (jumped to over 10dB). I convinced Sky to retry now that I had sorted out the noise, and I jumped to synching at 14.5Mbps, that has dropped to 12Mbps today but even so, much more what I would expect based on the attenuation for the line.
Just switched from Talk Talk business (nee Freedom 2 Surf) to Sky.