This could be the answer about the condition of Kapitanleutnant Fritz Steinhoff's grave.

As Vance's webmaster I have had contact with Steinhoff's relative who lives in the United States. It is possible they or other family members take care of his grave.

I search for U-873 information because USS Vance DE387 was the ship she surrendered to in 45.

Hope this helps with this question.