Received a less-than-great grade due to bad instructions. Should I appeal?
If you have already submitted the request for a regrade to the TA and instructor, then, for now, you've already done everything you can do at this time.

The real question here is how much this will matter at the end of the semester. Unless those points will take you across a "transition" point where the letter grade will change, it doesn't matter in the long run whether you get those points or not. So, ultimately, the need to fight for them depends on what weight those three points have. If the total basis is 1000 points, you're arguing about 0.3% of the total grade, and it's not likely to make a difference this year. But if it's 100 total, those 3 points become 3 percent of the total, and it's much more likely to matter.