Ok so take it one step at a time away from the battery.
Measure first at the battery take a note of the voltage reading between the + and - terminals on the battery. Then take a reading from the battery + to somewhere on the chassis, a decent earth point , somewhere like the fuel tank strap bolt.
Then from fuse 30 on the fuse box, there are two red wires. Measure from them to the chassis maybe the bolt holding the fuse box on.
Then the red terminal 30 on the ignition switch to earth.
Then put the red terminal 30 back on and measure on the terminal where the two blue wires are connected. Not the blue wires themselves but the actual spade connector they connect to on the switch measure to earth. (So red lead from meter to the blue wires terminal on the switch, black on the meter to earth on the chassis). You need to switch the ignition switch on to do this one.
Next measure at the coil, take the blue wire off and measure to earth from the blue wire terminal. i.e. Put your red meter touching the blue wire and black lead to earth. Then plug it in to the coil and take the measurement again on the coil +. Again ignition switch needs to be on.
Make sure you take an accurate note of all the results on a bit of paper and where they were taken. Then post them up.