Cosmological redshift comes from general relativity, not the SR Doppler effect. Local motion does produce a shift on top of that, but that's not all redshift. Nearby galaxies are actually blue shifted.
which says that yes, the greatest reductions in death rates were for infants and children, but for every group under 85, mortality dropped by at least 50% from 1935 to 2010.
which seem to say that those who are 18 today expect about 15 more years than they would have in 1900.
Not to mention nutrition, hygiene, and antibiotics are probably reasonably important in reducing infant mortality. I do agree that for an article specifically about aging they might have been more careful about those numbers, though.
The lectures are broken up into segments (which you might find convenient or annoying). There's not much more than that, unfortunately. If you want exercises, his problem sets are mostly from Kleinberg & Tardos, sometimes with problems from CLRS.