Nice work. The cab rebuild really did you a favour and improving your SNRm
Can you recall what caused it to get banded at 74Mbps? I can see a large spike of Err/Secs on Apr 12th after the SNRm had been running at 2.9dB for a while, but can't see if there were a lot of retrains. Banding seems a bit harsh for what on MDWS looks like a single bad day or Err/Secs.
The reason Im curious is that I've had much higher Err/Secs than you have and the only diff being that I can see from MDWS is that your SNRM was low.
You may have a point about needing a lot of spare SNRM, and why some suggest self capping. On face value it certainly seems to have been what did so on your line.