Your income does not factor into the equation. Only your husband’s income is considered, and he will be given a credit for the child that you have together. If your husband falls behind in child support, the mother of the child could garnish his wages or bank accounts, or lien the house.
If your husband’s name is on any bank, investment, or financial account or asset including the house, even if it is jointly titled, it can be attached.
The only accounts or assets which could not be attached are if those accounts or assets are in your name only.

Unless you have younger children for whom you are providing support, child support automatically ends on your daughter’s 19th birthday. If you have other kids, you will need to modify the child support.
You are correct. Unless you agreed in writing that you have to pay for college, you are not obligated.

Child support becomes a money judgment at the time it is due. Since you owe $23,000 in past due child support, the judgment stands.
If you truly have absolutely NO INCOME, you should contact child support enforcement or your ex-wife’s attorney, or whoever is pursuing the judgment, and advise them.
However, if you have ANY money available to you and you are not paying anything towards your arrearage, your ex-wife could file a contempt action against you and amongst other things, ask for jail time.
Therefore, you need to pay something, even if it is $10/mo. This shows the Court that you are not trying to shirk your obligation and are making a good faith effort to comply with the Court Order, despite your circumstances.
Assuming you have no income nor assets, and do not have the present ability to pay anything, there is not much they can do to you.