It's a long time since I had this kind of problem, but what you're experiencing isn't due to the ping time being a little bit high, it's down to packet loss (or at least very high delays, like seconds).
280 ms isn't great, but it won't stop you driving, and you won't get spectated because of "idle" just due to that.
When I had the issue, it was down to my ISP using "traffic management" which screwed certain packets (I was never sure quite which ones, could have been any combination of TCP and UDP on certain ports) when their network was remotely busy. Their game recognition software was designed to recognise game connections and ensure low latency but it couldn't handle LFS. I changed ISP, no recurrence.
Did you try disabling the network monitoring software you mentioned above, by the way?