Hi Johannes,
forum.valka.cz/topic/view/331/Stihaci-eskadra-52=1945
I do not know how reliable the above source is, but it has Oblt. Otto Karl Klemenz as the Staka. of 9./JG 52 from 15 Dec. 1944 to 8 May 1945 which suggests he survived the war. I am sure you will be able to judge its accuracy from the dates it gives for the other Stakas.
The Kracker site gives Otto Karl as a Hauptmann and Staka. of 11./JG 52. It gives his medals as EK 1 & 2, Wound Badge, Night Fighter & Fighter Operational Clasp. However, it also questions whether there are two men named Klemenz.
best regards,
Jim Geens