WoVo

There were rougly 10 different hooks for the 545, depending on thread thickness etc. Your hook/machine is set up for very thin thread (likely textile garment production), so no open notch. Likely max. NM 100 thread. Good thing: You could still get parts and adjust the 545. What thread are you intending to use?

The "bar" is the lever for knee or foot lift. Pfaff 27/28 and Adler 48 are very similar, you'll find the manuals online.

Very good machines indeed. The walking feet/needle feed versions of the Adler 105/205 and Singer 45K (and it's Seiko, Ferdinand and Cowboy clones) are a bit weaker (=more joints/moving parts) than the solid frame versions but useful for slippy materials and some kind of work like saddles.

A 205-64 is not a walking feet (-370) but a needle feed sewing machine. One of the best made in the class of super heavy arm machines.

Could you supply a picture of your tension assembly and thread at the point, where the needle eye just enters the fabric?

I might have some spare screws. Based in Germany. Actually your 105 has been rebuild to a 105-6 standart to work with a roller feet, does the presser feet rod have a flat and bolt hole? I might have also some feet.