Panic not, or at least not yet!
On my 1978 4/4 adjustment consisted of pulling outer casing of cable ,as seen in your photo, as far forward as possible until ALL SLACK was adjusted out, and then tightening the two nuts down to the bell-housing.
This removal of any free play in the cable at that end seemed counter-intuitive, but was totally the correct method.
Please try it, and see how you get on.
Andrew
Glorious Devon (especially today)
