@RightCoaster is right: the easiest way out of any ED problem is to accept Loyola’s offer and let NU know that you are not interested in being considered for ED.
ED is a serious consideration, and, yes, it can have some very bad consequences for those who do not understand what ED means. Do not apply ED if the school is not your absolute number-one choice. This is why one applies ED: to get the edge in admissions by promising to attend if admitted. At the same time, ED is not as absolutely binding as many on this site make it seem. For instance, St. Olaf’s enrollment statistics for ED are 90%. I highly doubt that the remaining 10% are all students who violated the agreement and got punished, unable to attend St. Olaf or anywhere else for the following school year. Things happen.
Every school’s ED statement is purposely vague. This is because there are dozens of situations that could make the ED situation complicated. As far as I can tell, the OP has not broken any rules. Applying ED does not mean that one cannot have other applications out there; however, if the ED acceptance comes through, one must withdraw all pending applications and not initiate any new ones. The OP is in a unique situation: he/she has already been accepted and, surprisingly, has already received a financial aid package (full ride) from Loyola. Despite the “Only for demonstrated financial hardship” line written in all caps in an earlier post, it might (I say might) be possible to argue that a full ride offer to Loyola versus 70K per year to attend NU is a financial hardship, even for a full-pay/high-EFC family. This is the sort of situation that ED is not designed to take into account: that one must attend at full pay even if another school has offered a significantly better offer (and the offer did not come after the ED acceptance).
That said, I’m not sure why this is a debate for the OP. If her/his family can afford NU, and if she/he loved it enough to apply ED, then why isn’t she/he Wildcat or bust? Again, take the full ride if it’s too good to turn down and let NU know that you’re no longer interested. Why risk taking the chance on whether or not NU would truly insist that a family turn down an already-offered full ride and pay 70K, especially when there’s an easier out?
Truth is, these potential problems could be eliminated if all ED schools would make it a rule that applicants cannot apply anywhere else ED or EA. Students will get accepted EA elsewhere (not a violation of many schools’ ED rules), and sometimes those EA acceptances could come with generous financial aid, something that the applicant and her/his family did not anticipate.