Regarding post-secondary education - at which degree level would the parenting plan end?

I don't know of a specific end-point to post-secondary education for purposes of parenting plans. It would be helpful to see the exact language of your parenting plan and child support order. Does it say that both parents are required to pay for post-secondary education, and is that term defined? Do you suppose that if you decide not to pay anything towards your daughter's Bachelor's degree that she will try to challenge you under the parenting plan? Do you think that the mother would try to enforce such a provision if she herself were not able to meet her obligation? If the answer is "no" to both questions, maybe you should just talk with your daughter about your financial situation and help her fill out the paperwork for some federal student loans. If the parenting plan or child support order does call for you to pay for college beyond an Associate's degree but that is proving difficult, you could always petition the court to have the paperwork changed, given your (and the mother's) current financial considerations.

Age 23 is the cut off, but I believe that you and the mother have the power to agree to modification of the support order to terminate post secondary support since post secondary support is not a mandatory parental obligation in WA. I also think you don't have to involve your daughter in the court filing. You should be able to file an agreed motion terminating support and mail it to the court along with the proposed order terminating support and the court fees and you are done. Its probably a $250 - $400 expense if you want a lawyer to do it.