I will admit I don't understand why the OP, or anyone else, would think this is a profitable venture. I would not spend the 7-8 hours/week for so little cash... not worth the hassle.
If you are seriously looking for advice - the answer is obvious - do the OT.
But there are a few pages of responses here where you try to justify your driving gig despite the fact that it doesn't pay well.
Your choice in what you choose to do for extra cash - but don't ask for advice if you're not going to listen...
If you want to get out and drive, get fresh air - there's nothing stopping you from going for a drive that doesn't involve food delivery.
Math is pretty simple in this case.