My cynicism about out "stink problem" was unwarranted.
Late last night I finally submitted our official notification that we had a problem. By today (a holiday, no less) the property management company had already notified the owner, who called and left us a very apologetic message.
Guess what? It smells like sewer because...it's the sewer! When the owner bought the house, she smelled it too. Turned out there is some capacity or fit problem between the sewer and the old house, so there is a filter that needs to be changed by the city every so often. And the time has come. The owner is letting the city know and we should be back in business in no time.
What a relief. The house will not collapse or give us mold poisoning (as far as we know.) There will be no opening of walls to investigate, disrupting our lives indefinitely. No mystery. A simple fix. I can't tell you how thankful I am.
So, hey! As soon as the city takes care of it, we are all set for visitors. You can even have a shower and eat a meal without fear of odor-induced nausea, unless my addled mental state leads to a cooking mishap.
It's nice to know that we can stay put and enjoy the things that originally made us excited to live in this house while looking for our next place to land. Fantastic.