The 1/250 setting has a separate, stiffer, spring. That's what makes it harder to set, and why it's good to not use it with the selftimer.
Try to put the button lever for the selftimer in the forward position so it blocks the cocking lever from setting the selftimer. Does the shutter work when you do that?
The Opton-Tessar is excellent. The "T" means that it is coated. The Solinar on your Agfa is a similar lens (four elements in three groups) but is uncoated and has front cell focusing. The Ikoflex with Opton-Tessar is most probably both sharper and contrastier and works well for both black and white and colour. And it's easier to use filters on the Ikoflex.