Inability to pay is not an excuse to liability under an agreement. If the note was breached and its otherwise enforcable, he will have to make some arrangements to pay the note or face a judgment which can result in other means of satisfying the debt, which often include the seizure of non-exempt property. If he hasn't already, he should consult an attorney and likely ask the court for a continuance for the purpose of consulting with counsel on the matter. It's not likely that the court will freely continue the matter at this late date, but it's worth asking.
Advice on this forum is for informational purposes only and should never be mistaken as a substitute for legal advice. If you are in need of legal advice, you should consult local legal counsel.
If he is being sued on the promissory note, the plaintiff may win a judgment against him, but based upon what you wrote, he has no assets which could be seized to pay the judgment (i.e. no house, no car, no wages). The judgment will last for 20 years, and if he has assets later in life, a patient plaintiff will come back and collect it when there are assets to seize. Filing bankruptcy could possibly discharge this debt, or judgment, depending on the facts (i.e. no fraud exists). As far as child support obligations, there is no way to avoid these or discharge them in bankruptcy.
Consult with an attorney ASAP.
I am an attorney who is only licensed in the State of Florida. My answer is general legal advice based upon what I perceive your question to be, and should not be relied upon because every person's facts and circumstances are unique, and because specific laws vary from state to state. To completely evaluate a legal issue requires reviewing and evaluating all relevant facts, applicable laws and other information. My answer does not create an attorney-client relationship, and offered for informational purposes only.
It sounds like it is a small claims case (under $5,000)? If so, and tomorrow is the pretrial, then typically the case will be referred to mediation. In mediation, the parties MAY settle, but cannot be forced to settle. Did he sign the note in his individual capacity or for the business?
I will include a link to an article on small claims procedure. I hope it helps.