Once you get this up and running, have a look at https://github.com/moeller0/lantiq_dsl_parser. This should allow you (with octave) to get some diagnostics and statistics out of your router from a machine inside your network, to plot SNR and bitloading over the frequency bins. Please note that this is work in progress that has seen zero testing outside my own VDSL2 link and will change in the future (as it currently queries way to much and hence also takes too long).
So, I would be delighted to get some testing done on a real ADSL link! This is a general invitation for testers.
To not highjack this thread any longer, I created a new topic for all discussion abou this:
https://forum.openwrt.org/t/simply-tool-to-query-lantiq-modem-statistics-and-diagnostics-useful-for-moem-routers-running-openwrts-dsl-cmd/53857?u=moeller0