Just found this. As you might have already suspected, Nathan's wife Johanna Jacobus died in Brooklyn in 1908.
Well... there happens to be probate records for her at the familysearch.org website. Her husband was the petitioner.
husband: Nathan Jacobus, 59 St. Felix Street, Brooklyn, NY son: William Jacobus, 251 Graham Ave., Patterson, NJ son: Theodore L. Jacobus, 255 W 116th St., NYC daughter: Sarah Engler, 680 Fulton St, Brooklyn, NY daughter: Rose Jacoby, 266 W 134th St., NYC daughter: Rebecca Braxton, Sea Cliff, Long Island, NY
My notes: -Johanna's 1908 NY Times death notice shows she was residing on Fulton Street, Brooklyn at the time of her death, she must have been living with daughter, Sarah Engler. -In the 1920 census there is a Theodore L. Jacobus, patient in a hospital on Ward's Island, NY, shows he was born in Buffalo, NY, maybe he died on Ward's Island.
Source. New York, Kings County Estate Files, 1866-1923 Name: Johanna Jacobus AKA name: Probate Place: Kings County, New York Probate Year: 1908 Record Type: Administration of the Goods, Chattels and Credits Name of Court: Surrogate's Court Record Category: Administration (without a valid will) Notes: Digital Folder Number: 004240812 Number of Images: 4 First Image: 452 Last Image: 455
If you register at the familysearch.org website you can sign in, navigate to the Kings County NY Estate Files and view the documents for yourself.