This far we have hit it on the nose every step going smoothly, but now the way you are talking we have hit the dreaded intermittent electrical problem.By the way I see no need to test the other connectors on the fuse box.

Look back at the power distribution diagram we have two things that can go wrong now. One the white wire with the yellow stripe coming out of connector C is intermittently touching ground and blowing the fuse or for some reason you pcm/ecm is shorting out internally some times.

You can do a couple of thing now
1. unplug the B connector at the ECM and see what the fuse dose(if it blows this will prove that the white yellow wire is touching ground)
2. trace the white yellow from the fuse box to the ecm looking for damage
3. just run a new white yellow from the fuse box to the ecm use the same gauge wire and some solder and heat shrink tubing(you could also use some butt connectors)

Lets say you run a new wire and it still blow the fuse probably a short in the ecm.

Ok so look at the diagram It says C15 this means connector C pin 15 all the views are from the back side of the connector so count and look for the white wire with the yellow stripe.

My 2 cents is on the white yellow wire.