Unless you're willing to go back into court for the purpose of modifying custody because you feel the children are being mistreated, you are on your own. The harsh reality is that for a case like this, going in without an attorney is like bringing a knife to a gun fight. Contact Prairie State Legal Services or other local legal aid organization for assistance.
Unfortunately no. Child support is intended for the basic necessities of life such as food clothing and shelter for the children. You cannot "track" it or insist that the money is spent a certain way. Child support is a fairly rough calculation replete with trade-offs to ensure that children have at least a modicum of support from their parents. One trade off is that the amount of support is essentially a basic percentage of net income for support, some would argue lower than it should be. Another trade-off is the one you identify - that the support payor cannot demand proof that the support money is actually being used to pay for the children's needs.
If you believe that a change of custody is required, you may need to bring a petition to make such a change. These issues are very fact specific and I cannot discuss any detailed info here since you don't provide enough information. You really need to meet with an attorney to address this.
The short answer to your question is no. You do not have the right to demand an accounting of where the money is going. If you believe the child is not being properly cared, or provided for you can go back to court and try to get physical custody changed to you.
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