I'm definitely not an expert on this, but i've been having a near identical issue over the past few days. You may want to check
my recent thread for a bit more information.
Looking at your SNR, when you capped and resync there was only a very slight increase in downstream SNR. I capped mine a bit more aggressively (~55mbit down to 40mbit) and saw a big boost in SNR on the downstream. Just over 4 days later, DLM resynced me and removed downstream interleaving.
Definitely try a much more aggressive cap. It looks like you dropped it from ~65mbit to 60 - try going down to 45 or even 40 if you can cope with it for a few days.