I'm not a trailer owner but this post intrigued me so without reading the entire thread, I am going to comment.
In California we have a law regarding "driving at the speed that is safe for the conditions", it means conditions may allow you to drive a higher speed or require that you drive at a slower speed than posted. For me at nearly 74 years of age and piloting around about 14K lbs of MoHo, cruising on an open interstate doesn't exceed 60, except to pass. With the towed attached, 58 except to pass. Two reasons, I don't want a ticket and I feel like I'm in control at 60 or under. On local roads I usually drive slower than the speed limit but fast enough as not to impede traffic.
I'm new to RVing, started in 1998, I have never had anyone show me their IQ or have to honk to get me to pull over because I'm blocking traffic. I also feel that the one or two unsafe situations I've been in were due to someone not knowing that I can't stop on a dime.
This has been a long way around for me to say to you, be reasonable and prudent and you will be safe.
Right now I am sitting in a hotel watching the sunrise with my granddaughter on the balcony asleep a, my grandson on the sofabed, my SDW(super darling wife) handing me the paper and imagining in the captains chair on my way someplace with friendly campers and good fishing.