Looks like you've tried a few things.
If the bitrate of the modem is changing, that has nothing to do with your PC... it's a problem in the telephone network, not your home Ethernet network.
Good:
140 Current Rate 1536 384
142 DSL Max Rate 1756 480
Excellent:
144 Current ATTN DR 4288 896
145 Current SNRM 22.0 22.0
146 Current LATN 48.5 31.0
Dunno:
148 Current TP 15.4 9.6
Incredibly Bad Download Rates for the excellent attenuation values:
140 Current Rate 224 384
142 DSL Max Rate 364 480
144 Current ATTN DR 384 896
Excellent, but bitrate is incredibly bad:
145 Current SNRM 18.5 22.0
146 Current LATN 46.0 31.0
Dunno:
148 Current TP 12.8 11.1
How far have you tried isolating the problem?
Your best way to deal with this would be to go back to the most minimal configuration you can... a single filter, single telephone (& answering machine) and the DSL modem, with a directly line out a window to the phone jack in the NID at the back of the house. Try that out for a day or two. If it still persists, try replacing the filter with another one and swapping out the telephone and/or answering machine. Basically, attempt to isolate it down to something in the telephone network and eliminate any device in your home from causing the problem.
If you don't have the time to isolate the problem yourself, you could have your DSL provider try a few things.
1) If you want a chance for more consistent performance, ask if they can put you on a "maintenance" profile (interleaving enabled.) This adds considerably better error correction and some latency to the connection, but if there is something interfering with the line, interleaving can sometimes allow the modem to deal better with the poor line conditions. If the problem keeps showing up even with interleaving enabled, tweaking the ADSL "software configuration" any further wont fix the problem.
2) Another alternative would be to see if they can turn on ADSL2+ at the DSLAM... very unlikely, but if they can, when a line problem occurs, ADSL2+ will dynamically downgrade and upgrade the speed based on line conditions. ADSL is very lame... if line conditions get bad enough to resync to a lower bit rate, ADSL will not attempt to measure line quality and automatically switch to a higher bit rate until a loss of sync occurs.
3) Ask if they have an IP-DSLAM (i.e. U-verse DSL) that can serve you. That might get you ADSL2+ or VDSL.
4) If you can isolate the problem to outside of your NID, ask if they can switch your F1 or F2 pairs. They may or may not be willing to do this, even if you can reasonably prove that it is not your equipment causing the failure.
Beyond that, if the source of the problem is out of your control (RFI) or an intermittent line problem, it will be a long and tiresome journey to locate the source of your problem.
And, if all else fails, make sure they know you are considering alternative Internet provider paths that don't include DSL... and be prepared to switch. If your ISP can't consistently provide the service you are paying for, that's something else you should make known as being unacceptable. Make sure you run some speed tests at »
www.broadband.gov/ too.