Is the salary earned from working for a company that invests in usurious banks, without direct dealing with these banks, unlawful? And is resignation obligatory, or the disbursement of the earned money?

If your field of work is permissible, and you do not directly engage in what is forbidden, nor directly assist in it, then there is no sin upon you concerning what you earn from it. The company's investment of its money in usurious banks does not affect this, as long as its capital or most of it is permissible. As for your salary and entitlements, it is obligatory to withdraw them and not leave them with the company for it to invest in usury, due to the hadith: "The Messenger of Allah, peace and blessings be upon him, cursed the one who consumes Riba, the one who pays it, the one who writes it, and the two who witness it, and he said: They are all alike." You can open an account in a trustworthy Islamic bank to invest your money.