That's perfect.  Use the same wing root line on the actual model to measure the downthrust angle of the motor mount.  It appears that the wing uses multiple joining rods.  If you block the fuselage up using the rods with packing blocks and shims to support the fuselage you can then use an angle jig to set the motor mount in place at the correct angle.

As to the wing's incidence it really doesn't matter since the so called center line is purely an imaginary reference.  The only angles that the air and model care about are the ones you just did and the simlar angle between the wing and stabilizer.   The measurements to the center line, when one is shown, are just a convention used by designers to have an agreed upon reference line to use for aligning all the parts. 

I've tried to say that the actual "center line" is imaginary and not important in the end in a couple of different ways now.  Hopefully it's getting through the language barrier?  But to answer your question no, that does not mean the wing is set to zero incidence.  It only means we are using the wing's chord line as our reference line for determining the motor's downthrust angle with respect to the wing itself.  Also do not confuse the purely fixed angle of incidence that the wing makes to the fuselage with the in flight angle of attack it makes to the air.  One is fixed by the designer and the other is highly variable depending on flying speed and wing loading changes that occur during turns.