What happened to Hjalmar Jakobsen?

I'm trying to find out what happened to my great-grandfather. He was born on 15 September 1896 in Ålesund, Norway. He was married in Norway to Karen Marie Jakobsen (born Hansen 12th august 1900 in Arendal, Norway). They had my grandmother on 11 June 1939. She was baptized 24th august 1941. I'm not sure if he attended, but left service at D/S Norse King in Boston on 30 May 1941, and began new service on 6 September 1941 in New York at the D/S Bencas (D/S stands for steamboat). During WWII, he was aboard the steamboat Dokka that was torpedoed, and the machine engine boat M/S Olsofjord that was hit by a minefield. He was aboard with several others. It’s likely he was injured/traumatized.

Our last trace of him is 11 November 1943, when he arrived in New York. The boat was M/S San Anders. I think he got amnesty. He never returned to Norway, where he had a small family. My grandmother is said to have been in contact with him through mail, but nobody can confirm this. I think he started a new life, perhaps he changed his name. I've looked everywhere, but there is no further information about Hjalmar Jakobsen.