If its that important to your grade, could you not shell out for the paid service until your project is completed? I'm assuming this is a semester project of some kind, and probably not terribly high-traffic, so it shouldn't be too expensive. I know it sounds like giving into extortion because it more or less is, but at 40% it sounds like a serious chunk of your grade that it might be worthwhile if you factor in the cost of learning to not rely on someone else's charity.

The last part isn't meant to chastise you. Twitter's API has long been free to access so it wasn't unreasonable to assume it would be so. But it has been true pretty much forever that you should not rely on someone else's goodwill and charity for a critical part of your project or business.

(None of this is to say that this change isn't being badly managed, just that I think you still have options here, despite being somewhat unpleasant.)