What if fuses are good but still won't start after hooking up jumper cables backwards?

Check all fuses for blown fuses because when you jumped it backwards, you created quite an electrical mess. With any luck, fuses is what were blown -- not other circuitry or component issues.

How LONG were the cables connected in reverse??? There may be major electrical damage. *TEST* - ‘ALL’ FUSES USING A TEST LIGHT. Good luck !