What is your source for him dying in 1943? Were there letters back and forth until 1935?
The 1930 passenger record said he was going to his uncle Ludvig Larsen in Brooklyn New York. Do you know anything further about him, that might help locate Konrad?

The 1940 census images were just released, but are not yet indexed. When they are, it will help to do a search to see where he was in that year.