Just read through your entire post, cool man. Hey, on your brakes, is your proportion valve hooked up correctly? I tried looking at your pictures but I couldn't really tell. Just to check, here are pics on mine in my 69 and a diagram to help.
My other "front" line out is plugged because I have a "T" down by the frame that separates the line so it can go left & right. You can plug one of the fronts to it and the other front comes from the left side (the way you have it mounted on your firewall) And the rear brakes would come from the top
This view shows the other front brake line, or in my case my only front line
And here is the diagram to better help.
Disregard my brake line Xing. I had bought the proportioning valve kit years before installing it and just never changed it. It never fit the "right" way like it was supposed to and I didn't want to buy a different setup since it works perfectly just the way it is.