Did you not secondary it? Next time, let it ferment out all the way then rack it to a secondary then add the berry's. 1.022 is too high and the yeast had a second little shindig that created your sour off flavors. Simple syrup will work, make sure it's sanitary. You can get brewer's glucose solids that would be appropriate. Just be careful with the sugar, maybe add more berry's to the keg or you may have a big alcoholic jolly rancher beer on your hands. Hope this helps and you save her, cheers.