Hi Jakob,
I am living around the corner in northern germany (7a/b). I am growing 2 jujubes, sold as li and lang, though I now suspect em to be just seedlings. If there is no dieback in winter, they do flower but in 10 years never set a single fruit. Dont know if varieties would be different.
The black apricots I grow are Vesuviano, Nostrano, Gigante di Budrio and Bolognese. In taste they resemble more a plum than an apricot. They produce more reliably than apricots.
If you like sour cherries I can recommend Jade, nice large and tasty fruit for fresh eating even. Needs to be pruned annually because it will develop blind wood otherwise.
In Pawpaw I grow Prima1216 too. It fruits ok on its own, but then needs help with pollination (brush). I also grow Overleese, Mango, Prolific, NC1 and some seedlings. None has fruited as early and reliable as prima1216. Prima is ripening quite late though, in mid october.
You could ad an aprium. I grow cot’n candy and tasty rich. They didnt fruit yet, plus your climate will be challenging for apricots and apriums alike. Don’t you like prune plums as eg Toptaste or other? I’m a fan and would always ad them. You do already have some plums though.
Hardy kiwi are good too. They need a structure to climb though.