Is it permissible to return to work in the Islamic branch of a Riba-based bank, despite it being "Islamic in name only but based on Islamic principles," due to personal and general economic circumstances?

Since you have learned that the aforementioned bank branch does not adhere to Islamic dealings despite its naming, it is incumbent upon you to avoid it and seek another lawful job. You will find it if you fear Allah and supplicate Him with sincerity and devotion.