Anyone growing or know of someone successfully growing and harvesting jujube's in the midwest?
Don't know, but I knew a guy who planted rubber bands & within a year was harvesting tires.
You could ask on the fig (Ficus) forum. Some of those guys might be able to help. It's hardy enough, but you might have trouble with photo-period, i.e. too short of days & not a long enough growing period. If you're intent on trying it, you should try to find a tree on its own roots. Those grafted, sucker horribly from the roots & present a continual chore to keep the suckers from draining vitality/vigor from the tree, much like Corylus avellana 'Contorta' (Harry Lauders walking stick) does. Just my thoughts.
Ridge Road Nursery, bordering zone 4/5, has them growing.
Here is a link that might be useful: Ridge Road