Kansas City Fed article. Doesn't answer all the questions.
Info on the writer.
Didem Tüzemen is a Senior Economist in the Economic Research Department at the Federal Reserve Bank of Kansas City and the Executive Director of the Kansas City Research Data Center (KCRDC). Ms. Tüzemen joined the department in July 2011 after earning her Ph.D. in economics from the University of Maryland, College Park. She also holds a B.S. degree in physics and a M.A. degree in economics from Bogazici University in Istanbul, Turkey. Ms. Tüzemen's main areas of research are macroeconomics, labor economics, and health economics.
https://www.kansascityfed.org/research/economic-bulletin/how-many-workers-are-truly-missing-from-the-labor-force/
As of March 2022, the U.S. labor force participation rate remained one percentage point below its pre-pandemic level. After accounting for the effects of slower population growth and the aging of the population in the past two years, I estimate that around 2 million workers are missing from the labor force. Individuals age 65 and older, whose participation rates remain persistently below pre-pandemic levels, constitute most of the missing labor force.