No rotten tomatoes here. (Mine are still green.)

I have also expressed discomfort in being relegated to the use of the estimate of radon-induced lung cancer deaths in 1995. Bruce, I think your summary is reasonably fair and your question is a good one to ask. However, I would not be so inclined to lay blame on EPA. Over the years when funding levels have continually decreased in real terms, and have long been under threat of being zeroed out, I recognize that EPA radon staff have had to work hard just to keep the radon program alive and functioning. While I'm sure they would also like to improve the estimates, to do a scientifically defensible job of doing so I'm afraid might require resources that they simply do no have.

Bruce, you hit on the right factors, I think. I would also add the evolution of indoor environments over the decades in terms of what radon levels turn out to be under current air-exchange characteristics. As you know, there are indications that the old EPA indoor radon data may be underestimating current values.
One other point: The EPA 2003 report discusses the risks associated with only residential radon exposure. While collectively smaller, risks associated with exposures in schools, workplaces, other indoor environments, and even in outdoor air, are not zero. I have attempted to make estimates of lung cancer deaths from radon along the lines that Bruce asks for, and taking into account all such environments, but I will be the first to emphasize that these have been "back of the envelope estimates by a non-expert amateur."

People such as Dr. Bill Field may be able to add more about thinking that has been done since 2003 on the issue you raise. For example, see the relatively recent study at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4768325/ even though that study's conclusions about US lung cancer deaths from radon haven't yet, to my knowledge, been adopted as better replacement values in any widespread way.