The two cents of someone familiar with the Fordham area, currently living in Brooklyn:
If you don't limit yourself to the subway and are disciplined about train times, you can do the trip via subway/MetroNorth (which drops you right at the Fordham gate) in about 1-1.25 hrs. It's a bit pricier, but if you're not traveling at rush hour MNR is MUCH cleaner, more reliable, and a better environment for getting work done while commuting. I know nothing about your field and obviously the question of parenting complicates the decision further, but I do know grad students who have a similar commute and manage.