Can my wife’s ex-husband dismiss childcare expenses he owes her and ORS, if he submits them as debtors in a bankruptcy hearing?

While I would generally agree with Mr. Whiting's responnse, the quest for more information is in order.  What is the nature of the Bankruptcy which has been filed?  Chapter 13 or Chapter 7?  If a chapt. 13, they may be handled quite differently.  If the expenses are for past due amounts, the debtor (ex) could propose a repayment over the life of the plan.  If they are for current and ongoing expenses, they must be included in the budget (schedule J) of the schedules and included in a plan

Yes, you should attend the meeting,and make known to the case trustee your issues.  He will probably give the same advice as I am about to; seek counsel!  You may, depending upon State law, be able to recoup attirneys fees from the ex.  Good luck>

A debtor cannot discharge in bankrupcty a debt incurred, "(5) for a domestic support obligation, [or]... (15) to a spouse, former spouse, or child of the debtor and not of the kind described in paragraph (5) that is incurred by the debtor in the course of a divorce or separation or in connection with a separation agreement, divorce decree or other order of a court of record, or a determination made in accordance with State or territorial law by a governmental unit."  http://www.law.cornell.edu/uscode/text/11/523