The diagram on the left shows the connections for deriving v.s.w.r. You have to make two measurements with the slotted line. One of the highest and one of the lowest voltage.
Not knowing what make and model your voltmeter is, it's impossible to say how it reads v.s.w.r. The manual will tell you.
your questions and drawings are really too vague to be able to give an informative reply
how about some actual photos of the system you are using so that we cam maybe get an idea of the equip.
some makes and models would be really helpful for us guys to be able to help you