I believe Kitz is calculating the loss due to your roughly 60 tone gap which has been been discussed a lot previously.
That would be in addition to the value estimated from your Hlog wobbles. You could do the same type of calculation that Kitz illustrates on your SNR wobbles, at a glance of the area involved you would, as expected, get a similar value to the attenuation estimate.
In total you may have a missing 2Mb/s due to the gap plus 1 Mb/s due to the wobbles.
On the wobbles B'cat suggest the most usual explanation but anything that gives a change in impedance along the line would also give it. Different cable gauges, a little resistance at any joints or several joints and other things e.g. in my case two metal paths within the exchange building. Such wobbles occur on a large fraction of lines, especially where wiring is older, generally they are never fixed unless the impact is very much larger than you case. Those case have large impedance changes that engineers have some chance of locating.
