Family seperations was a moral blow, but his approval didn't drop in the midst of it, it kept rising. Mainly because it highlighted the hypocrisy. Family seperations are wrong, sure. But trafficking is a legitimate concern, illegal immigration poses far more danger to children in terms of death and rape/assault.
If you want to make that a narrative, you're going to need to provide evidence for it. Here is strong evidence that the separations issue was not connected to the rise in his approval rating:
Simply put, a policy unpopular with the overwhelming majority of voters is not going to make one's approval rating rise, generally speaking.
You can throw the idea that it "highlighted hypocrisy" out there, but if you don't have anything backing that, it doesn't even qualify as an argument. Otherwise, this is just an abstracted whataboutism.
We can argue about the demerits of his immigration policies in another thread (though that you think that it's bad parenting to take a chance on a better life rather than a certain suffering is questionable; why do you think undocumented immigrants take such a perilous journey to get here? If I were a parent in that situation, I'd choose the same way), but I think the effects of family separation clearly are not what you think they were.
The other confusion you seem to have is conflation of progressives and the Democratic party. "Abolish ICE" is coming from the most liberal states in the Union--California and New York, for instance. There are liberals in other states. It would be akin to describing the Republican party by the actions of Mississippi, when the most popular Republican governor in the country is in Massachusetts! Obviously the Republican party as a whole isn't as liberal as Baker, but if you describe either party at its most liberal or conservative, you're going to create a picture that is alien to reality. There hasn't been much polling done on this; all I could find was this, at the height of Trump's family separation policy crisis https://www.politico.com/story/2018/07/11/immigration-ice-abolish-poll-708703
Given the context of the poll, the support is probably lower now than it was then. I'll grant you that it gives a plurality of support to pro-abolish Democrats, but it also shows how divisive the issue is, and therefore probably too politically toxic for any Democrat to touch in the primaries and 2020.