My guess is that the professor will not make an exception. Like you said, there are plenty of other people who are working tons of hours outside of class, like people who need to pay college expenses without parental assistance. In the professor’s mind, if they make an exception for you, how is it fair for other students who also have grueling schedules? What’s the point of the grading scale then? Knowing your limits and balancing course load with outside responsibilities was your responsibility to manage well.
I think you can still ask (respectfully), and focus on how much you have improved. Try not to come off as if you are entitled to the B-. I would keep my expectations low, imo.