I reckon that line is good for at least 1600-1700kbps sync on ADSL Max, with an IP Profile of possibly 1.25Mbps (effective sync).
The site I use to check that sort of estimate seems to be down at the moment.
Against that estimate is the high number of error seconds.
Every second is errored, yet that isn't mirrored in the actual error stats. Odd.
Have you ever
checked your phone wiring? That can make a big difference to a line.
Are you absolutely sure nothing is connected to the phone line without a filter, such as a Sky box or burglar alarm?
Is there any chance you could plug your filter into the test socket, (that's the one at the back that the faceplate plugs into), and get the stats from there after say 15 minutes like the ones you have posted? Then do it again with a different filter if the error seconds are as bad.