Is Zakat obligatory for someone burdened by heavy debts who claims poverty? Is settling debts more prioritized than Zakat? And is caring for a mother and a disabled brother considered charity?

Borrowing with interest is unlawful (haram) according to Islamic law, as it constitutes usury (riba). One must repent from it and not return to it.

The money paid by your disabled brother must be returned to him, as he is weak and in need of the money.

There is no zakat on the car and the license if they are tools of a profession.

Spending on a poor mother is an obligatory expense (wajib) in Islamic law and not a voluntary charity (sadaqah nafilah). If you account for it as such, it becomes charity, and you will be rewarded for it.