In the state of Illinois how can a non residential custodian get residential custody?

My husband has a joint custody agreement (since 2010) naming him residential custodian. Currently he has his daughter Friday-Tuesday. In 2012, he married, obtained full time employment (at the time of the papers being filed both parents worked part time and lived at home with their parents) and moved out on his own. His daughter’s healthcare, speech/OT are all taken care of by him at our location. His daughter's mother is 30, still lives at home with her parents, sends her daughter to daycare (even when she isn’t at work), fails to utilize her full visitation periods, and continually subjects her daughter to second hand smoke. Unfortunately, mother has failed to take her daughter out of her families smoking environment. Additionally, my husband is the one that obtained an attorney to create the initial joint custody agreement. She failed to obtain an attorney and just signed the papers. My husband has had a change in circumstance and we would like to petition the courts for child support (reserved the first time around) as well as change her parenting time as we drive over 240 miles a week to drop her off to her mother. It is a very unstable environment. She is currently enrolled in an accredited pre-school at my husband’s location. If my step-daughter's mother decides to fight the change in visitation (every other weekend and sometime in the summer) and we also petitioned for child support as it was reserved the first time, does she have a chance? I guess I am asking how does a non-residential custodian obtain residential custody in the state of IL?