Seeking records for my great-uncle (WWII German POW)

My Great-uncle Werner Knab was captured by US Forces in North Africa in April 1943. I have managed to get some basic information about the camps he was in. However most records don't have exact dates. I am hoping to locate prisoner lists and other camp records which may have my great-uncles details on them. But where do I start? He was captured in Tunisia on 11 April 1943. By 8 June he is listed in Camp Hearne, Texas. On 18 November 1943 he is still listed in Camp Hearne. On 16. November 1944 he was transferred from Camp Wallace, Texas to Camp Mexia, Texas. But when was he moved from Hearne to Wallace? In March 1946 he was sent to England, where he stayed for a further 10 months before being released. However before being released he was once again transferred into american hands on 6 January 1947. He was then listed in a weekly list at Dachau on 22 January 1947 which was his release date from being POW. Why was he released via Dachau? Dachau was in the US zone in Germany, but his home was in the Russian zone, which is where he returned after his release. My great-uncles POW number was 8WG-5017. Most of this information I received from the German military records and the red cross. I am hoping someone can point me in the right direction of where I may find any records relating to his time as a POW, what interrogations may have happened and what he may have been involved in.

Thank you in advance, Stefie