If I understand correctly, the OP is trying to turn a necessary trip into a quasi-MR by throwing segments or creative routing between two endpoints and dates that aren't as flexible as a true MR. The thing to remember is that for every extra degree of inflexibility, one must be prepared to accept a proportionally higher cost per mile. Whereas a true MR could be done for <3 CPM, expect to pay 4-5 CPM (or more) for your ticket.

I do this often, and I generally have an idea, based on the endpoint cities, of what connecting cities to search for in ITA. I use milecalc.com to check the mileage for several different routings, then I return to ITA to find the 2-3 best fares for my preferred route. Then I check the fares for my second favorite route, and so on, alternating between ITA and milecalc to find an optimal solution. In the end, it's all a matter of one's tolerance level for inconvenience, mileage needs, and the constraints of the "real" reason for the trip in the first place.

Flying out of NYC, I can generally count on throwing an FLL, MCO, or PBI connection into my trip, which can pile on the miles quickly. Your XNA & CID endpoints are extremely restrictive, however. The best you can hope for is probably ATL, MSP, and/or DTW in the mix. Good luck.