TLDR?
600k males btwn ages 20-60
Approx another 600k in other age brackets. Total males 1.2mm
22k firstborn males into 1.2mm is approx 55 children per family.
Life expectancy in moshes time was 70 years. Assuming Max of ten pregnancies per mother in mitzrayim. Equals pretty much on the button 6 babies per pregnancy.