The first point could too - modern technology has turned a number of conditions that were extremely serious in the wild into mere annoyances. Myopia, asthma, newborn jaundice, hernias, both high & low birth weight, obesity - all of these could easily be fatal if you (or your mom) needed to outrun a lion, but they're easily taken care of with modern medical technology, and hence have become extremely common in the general population.

And yet, the population isn't exploding in developed countries. This implies that something else must be receiving the selection pressure instead. I wonder what it could be?

Economic ability to pay for these medical treatments (well, in the U.S. at least), as well as all the other things needed to keep the lions away from the kids. There's a big fertility bust among what used to be the middle class, as many people don't see how they could possibly afford the necessities needed to raise a child (health care, housing, education, safe environment, parental attention) as they were raised.

(I suspect that there's also simply less selection pressure, in the sense that more people are having 1 or 2 kids, vs. in historical times where the emperor my have had 1000, a wealthy man dozens, and lots of paupers ended up with no kids at all. That has the effect of letting lots of genetic variation into the genome without immediately weeding it out, at least until some selection event occurs in the future.)

It could, but it would be a much weaker form of control that could be bypassed (by fleeing the city to the hills to reproduce freely, etc.). If you need an IVF lab to reproduce, it'd be much harder, perhaps impossible to escape the controls.