Wow, that sucks. Generally, there are some pro-bono legal aid places in every city that will help you with stuff exactly like this. I lived in one state where you didn't have to pay rent if your heating was broken and the landlord had a certain period of time to fix it.
I don't know exactly what your issue is, but if the landlord can fix it and is not doing so then it is most likely illegal. For sure consult with a lawyer.
Also look here too https://www.washingtonlawhelp.org/resource/your-rights-as-a-tenant-in-washington
I'm sure there is some good information in there.
The new credit monitoring for rental applications is straight-up BS and I do not support such things at all. It's a great way to keep a lot of good people down. Maybe you can only have your fiance apply for a new place? I don't really know how to help with all that.
Good luck and let us know how it works out.