Is it permissible to work in an interest-based bank in the Gaza Strip due to necessity, knowing that the salary is very low, and if another job opportunity becomes available, should I leave this job?

Dealing with usury (riba) and assisting in it are among the gravest of sins. It is not permissible except in cases of dire necessity, and what you mentioned in your question does not permit you to work in a usurious bank. Allah Almighty says: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect. And whoever relies upon Allah - then He is sufficient for him. Indeed, Allah will accomplish His purpose. Allah has already set for everything a [decreed] extent." {At-Talaq: 2, 3}, and His saying: "And whoever fears Allah - He will make for him ease in his matter." {At-Talaq: 4}. And whoever gives up something for the sake of Allah, Allah will compensate him with something better.