Is it permissible to work in a usurious bank with the aim of buying agricultural land to protect the family from potential economic disturbances, or is that considered self-destruction, and is entrusting the matter to God more fitting?

Usury (Riba) is among the most severe prohibitions in terms of sin. The sin is not limited to the usurer alone but extends to everyone who assists them. In Sahih Muslim: "The Messenger of Allah (peace and blessings be upon him) cursed the one who consumes usury, the one who pays it, and its two witnesses, and he said: 'They are all equal (in sin).'"

Working in usurious banks is forbidden because it involves assisting in usury. It is not permissible to commit something forbidden based on an assumption or expectation. The avenues of lawful earnings are many, so do not embark on the forbidden without necessity.