If you are simply an authorized user on an account, you are not considered an owner or responsible for that account. Therefore, it would not be a part of the bankruptcy. The full owner of the account (your mother) would in any event remain responsible for all debts on that account.
As for the house, as a secured property, you would have to reaffirm your obligation on that debt or the bank could foreclose on the property. The only other option would be for your ex-husband to refinance in his name only. If he cannot do that, and you did not reaffirm the debt, the bank could foreclose.
The other issue you will face with the house is if you are listed as a co-owner, other creditors might try to seize the equity
in the home since you are only entitled to up to $15,000 in equity on a home in a Missouri bankruptcy. If you can show that your ex is actually the sole owner of the home at this point, he can avoid becoming entangled in your bankruptcy. But if you remain listed as a co-owner, you can expect a fight over that.
I hope this answers your question.
Please keep in mind that information in this forum is for informational purposes only. It is not legal advice and does not constitute creation of an attorney client relationship. Before acting on any such information, you are always advised to consult with an attorney licensed to practice in your jurisdiction who can take the time to review all the facts and laws relevant to your situation.