Looking at your pbParams stats, it is clear that your connection can only use some of the lowest frequency downstream band D1.
Signal & Line Attenuation is 35dB or so for that band in which a little less than 500 bit-loading tones are useable.
These lower tones are at ADSL2+ frequencies & with attenuation of 35dB, the Kitz ADSL calculator suggests a line length of 2.5km & a sync speed of 11712 kbps.
Even the typical attenuation of 13.81 dB per km, used for 0.5mm copper in calculations etc. suggests 2.5km or so line length (from the cabinet for FTTC).
I have attached the graphs from a 1600m or so connection for comparison purposes.
Again, only the lowest frequency D1 band is useable.
However, sync speed is much higher than on your connection.
I notice your DS TX Power seems quite low which no doubt has some effect on sync speed.
Mine is usually around 12dBmV to 13 dBmV over around 1000m & the graphed example reports 11.1dBmV.
If your cabinet is a long way from the exchange, nearby ADSL signals will already have weakened due to the copper distance from the exchange.
So to avoid your own FTTC connection drowning them with crosstalk, it could be that your power levels have been reduced accordingly, thus lowering your own sync speed.
There may also be other factors to consider such as very high error counts, high Interleaving depth etc.
Would it be possible for you to post a copy/copies of your xdslcmd log(s) for us to have a closer look? Windows or Linux format would be O.K.
The Windows version of the scripts also uses "xdslcmd info --stats" for data.
It would be good to include that too.
All the relevant data results in a Windows log file of around 330KB in size (too large to upload to this forum).
However, zipped, the filesize is around 61KB, so can be uploaded here.
I have to admit that I have no realistic idea what FTTC sync speeds you should expect for your line length (assumed 2.5km).
However, I would have thought it could/should be a little better than you report.