if you have no idea about what you want to do with your life, go to industry to work first. It may expand your horizons....there may be things you want to do and you never even heard about it at this time.
since you have applied PHD and you have got offers, I think your intent was to pursue a PHD .You have worked for so long,so why not try another way of life?If I were you ,I'd be quite contentto accept the IIT offer.By the way , do "Niu" schools require working experience and MASTER degree as a prerequisite of giving PHD(especially finance) offer?