3/16" is what I thought, thanks for confirming
The nuts aren't junk, and if they are the same size as the thread in the caliper then they are m10-1.5.
Sitting here without the line in front of me I don't recall any sharp angles, nothing over 90 degrees anyway. If I use the poly I'll have to join on the middle which seems easier to me than trying to run one solid line all the way down and behind the engine to the other side of the car.
Thanks for the info!