Glad you found the instructions and have it sorted. It is definitely not right in the pictures, but a different manufacturer to mine so was not easy to see what should be done. Perhaps a picture of how it is now would be of interest to all.
Yes, it is definitely wrong in the pic. It should be a cascade purchase. The line that goes through the sheave at the top of the vang should not be tied back on itself. One end should be attached to the lower floating block, and the other end should go through the top sheave and back down to terminate somewhere at the bottom of the vang. On my vang the termination is done inside the vang, so it is possible yours was originally like that as well. Perhaps it broke so someone just tied it off. The rope that comes from the cockpit goes through the turning block at the base of the mast, up through the floating block and back down to terminate at the base of the mast on the other side of the vang. (Unless you want to have vang control on both sides in which case you go through another turning block and back to the port side cockpit.)
Unfortunately I cant find a pic of my boat that shows the vang clearly.
Here's a picture of ours, although a different brand of rigid vang. The cascade wire goes inside the vang to a sheave at the top.
The block and tackle arrangement can have different purchase depending on the need. We only have 3:1, but we tension it with the halyard winch so it's OK.
Yes, that is the same as mine, except we only have 2:1 pulling on the cascade for a total of 4:1.
I'm sure I will upgrade the purchase on my vang at some point. That is one thing that really annoys me about my boat...everything, even the vang and traveller are winch-dependent in any but the lightest winds!