One of the issues with these types of accounts is that the IRS provides no clear guidelines of how the account assets may be used for the benefit of a child. Here is how the rules
"A custodian may deliver or pay to the minor or expend for the minor's benefit so much of the custodial property as the custodian considers advisable for the use and benefit of the minor, without court order and without regard to (i) the duty or ability of the custodian personally or of any other person to support the minor, or (ii) any other income or property of the minor which may be applicable or available for that purpose."
Basically this is a very broad rule where the botXXXXX XXXXXne is that the expense must be for the minor's benefit. In the case of medical bills, this would obviously be a benefit for the child. However, in the case of child care expenses, here again while that is an indirect benefit for the child, it is really more of a direct benefit to the parent who needs the child care services so that they can work.
You would be safe to use the funds for anything which was of direct benefit to the child, such as medical bills, clothing, education, etc. So there are a number of things that you could actually earmark as being of benefit to the child. Since your ex husband is the custodian of the account, he would be the one who needs to make the withdrawals. If he does make withdrawals to cover some of these allowed expenses, it would still not relieve him of or reduce his child support obligations.
If this was helpful please press the Accept button. Positive feedback is also appreciated.