That's a rough patch, it seems. Sounds like you handled it well. I think acknowledging the driver was appropriate. Sometimes I hold up one finger indicating please wait one minute. And then when I turn off I wave indicating thanks for waiting.
I've got a stretch like that but fortunately there is a traffic light involved at my right turn intersection so I get a jump on the cars (except for the few that are turning with me. I have in the past did the 3/10 mile stretch out of the saddle kicking it as hard as I can. It';s kind of a fun finish to the 13 mile commute. Fortunately this past winter during a flooding storm I discovered there is an alternative that is no longer in distance so I don't ride on Route 9 in Natick, MA until it's time to go home. Then it's the old story in the other direction.