I understand money is tight for a non-profit, but why are bandwidth costs a gating factor?
Both your upstreams, Cogent and Hurricane Electric, offer 100G ports at fiveish grand per month in carrier neutral DCs. Given that your budget is in the millions, an outlay of this magnitude doesn't seem wildly out of the question.
If you can explain what the problems are in getting more bandwidth, I'd be more than happy to see what I can do to help.
Please let me know if you'd prefer to discuss the matter over email.
Can you ping me by email?