Based on what you have said so far, I would say you (or more accurately your parents) cannot afford Cornell. Go to Waterloo and look to transfer someplace else next year.
I don’t think appealing to Cornell for aid is really proper - after all you applied ED on the premise that you could afford it. Plus, I doubt much will come of it.
I am not a fan of a gap year which is essentially a year wasted in one’s academic/social prime. I think that is especially true in your case in that the only reason for taking off a year would be to go to a more exclusive school later. You might not even be accepted given the vagaries of selective schools. Plus, all of the selective schools will cost about the same as Cornell so there is no value in waiting.