Thanks to my friend Åsa I now have a plan! (A "plan" as in - well, you'll see)
It turns out my DFW is a modified Mager clone.
(Who Mager is? Wait and see, I'll have to read the whole book first.)
It also appears that is it a flyer-lead, bobbin-drag (is that "Irish tension"? I always get confused about the brake type wheels and their terminology).
But there is still one mystery...
Here is the overview of the construction drawing:
The tensioner pulley should be mounted top-down, and apparently wedged in place. (Though the wedge can't be seen, but there is no other fastening shown either)
Two detail pics:
This explains two mystery holes I have - where the green arrow is, mine has holes on both sides. BUT: there should be holes where the red arrow is - holes pointing forward.
On the right-hand maiden (is it called maiden even if it is an integral part of the structure?) there is a hole on the outside, but on the left side there is no hole at all.
(And: "maidens" or "uprights" - they seem to be one and the same piece of wood going from the table to the top. No way these "maidens" have been/can be made to turn!)
Speculating: can it be that there is just ONE brake-band, braking both bobbins at the same time? It would, I think, make the adjustment easier?
(And I still haven't made the axle retainers, so I can't try it out. Yet.)