Can't tell if you have any rubber in that sandwich of nut washer fork washer nut.
you need some so that the slave cylinder isn't providing all the misalignment compensation as the fork travels its arc...its the expensive bit id want to give it less of a hard time...
id use a standard z bar manual clutch rubber insulator and curved face washer, you will not need the nut or washer on the back side of the fork, if you install the standard return spring.
you may need to bore both new parts out a bit to fit the threaded end of your pusher slave.
curved face of washer faces clutch fork eye with the rubber insulator pressed into the eye and resting on the curved face of the washer
double nut to act as stop of the washer position on the threaded rod under the washer
back of fork needs nothing but a 1/2 inch of the threaded rod sticking through to that side to keep it in...
this will allow for the misalignment at the ends of travel when the pusher shaft is not perpendicular to the eye in the fork.
i have not done this but have seen it done a number of times by people using 3 series BMW pusher slave units, in a similar way to the mounting and set up of yours.
this unit
FEBI BILSTEIN 01000 Clutch Slave Cylinder Fits BMW 3 Series 5 Series 6 Series Z1 | eBay UK
the australian version of the insulator and washer will fit right on the US version has D shaped hole in the washer that will need to be made round.
id also still use the return spring that pulls the lever back, i can see the small cut out in the clutch fork arm has no spring on it, this runs up to the bellhousing side and pulls the arm forward gain to lift the throwout bearing face just a way from the clutch so it doesn't constantly spin with the action of the engine.
check out this
Fits 66 67 68 69 70 B-Body Clutch Rod Service Kit Big Block and Small block | eBay UK
see profile to face of rubber. that fits into the eye on the fork and holds the insulator in.
see big washer that has D shaped hole. bore that hole and use washer curved face to push against rubber in fork.
use the two nuts you have to act as a lock/stop to position the washer where you need it.
You will need the correct return spring the spring hook length depends on application which depends on bellhousing used and clutch fork. the bell housing will have a cut-out or cast in "Thumb" to receive the bellhousing hook-end of this spring .
the other end hooks round the fork and has the end of the hook ride in that tiny cut out, visible in your second and 3rd pictures...
Dave