"... so I like to ride a bit off the line to indicate to drivers that they won't be able to safely pass me without crossing the double yellow line. This is is really important when there are oncoming cars--by riding out in the lane, I'm trying to tell drivers that they'll have to wait behind me until oncoming cars pass...it has always just seemed safer that way."
I'm sure we are all seriously glad that you and the truck driver are OK.
That being said, I think you are very fortunate that this "manbearpig" in the wife beater t-shirt had enough forebearance and judgment to make a fast decision and choose to risk his property and his personal health and safety by running off the road almost into the trees in order to avoid clipping or nailing you.
However, from your narration it seems you almost might prefer to have hazarded a different outcome if only the driver was a classier guy or gal more worthy of your respect.
Seems you feel it would be better to have risked an alternative ending if only the driver was a nattily attired totally fit self-centered yuppie broker in a pristine classic convertible Jaguar or DB9 . Of course, such an egocentric individual might have hesitated just a hair too long in weighing the choice between totaling their pride and joy and maybe being decapitated in a rollover versus clipping/creaming an unknown bicyclist riding in the middle of a fairly narrow country road.
"If I had been riding right on the white line and this guy had tried to squeeze between me and the oncoming traffic, he probably would have hit me with his mirror or, certainly, with the trailer he was towing."
So, exactly why do you intentionally choose to ride on a road like this? You've accurately detailed all the probable contributing factors, but by your own admission, the most significant contributing factor was your own personal decison to engage in a somewhat risky behavior.
We all make errors in judgment. But, perhaps there are wiser behavioral alternatives than ... "I'm playing the odds, I guess...I think that's all I can do."
The fates seem to have given you a second chance. Use it wisely.