re: Been living in a house that has a radon level of 11.6 pq/L for 20 years… am I screwed?

Those 3-5 day tests don’t really tell you that much. Your situation could be much better or worse as the levels fluctuate with weather events and time of year. Rain events will spike levels and the levels are typically higher in winter.

I’ve been tending the levels in my basement for years with a digital logger and have learned a lot. We installed a mitigation system and it has taken us from a mean of 5 pCu/L to around 3. When it rains and we want to be in the basement we will open windows and within several hours get down to 0.4 which is about the level one will observe outside.