In The Same Boat I live on Hwy 6, 3 miles from Iredell and about 6 from Hico. Ever since the rainstorm that came through right around New Years I started having the evening slow speed issue.
Had this service for nearly 4 years and it has always been fine. Support is useless, and there are no other options as you are aware. I've been putting together piles of speed tests, ping tests, diagnostics in the hope that if I ever get anyone knowledgeable to talk to, I can make the case. Honestly though, they know what the issue is and they are lying about it. Not sure what we can do about it though.