The main feed semi-randomly decides what it thinks you want to read

You can make it less random by viewing in chronological order. You do that either by appending "?sk=h_chr" to the main Facebook URL, or by selecting "Recent First" rather than "Top Stories" in the little dropdown near the top of the left sidebar whose name I forget.

(In case it helps remember the cryptic string of characters: "?" in a URL introduces parameters, and is followed by something of the form key=value&key=value&key=value; in this case we have only one key/value pair; "sk" presumably stands for "sort key", i.e., the attribute of a feed entry that will be used for sorting on when FB decides what to show you and in what order; I don't know why "h_"; "chr" is clearly short for "chronological".)

I am not sure whether in this mode of operation FB always shows you all the stuff you are potentially interested in in chronological order; my guess is that it still filters it in some undisclosed way. But it's at least a bit more deterministic.

(I agree with all you've said here about Facebook.)

you can't easily tell it to remind you later

You can save a post for later reading from the dropdown menu to the right of the byline, though you'll still need to remember to check your saved posts once in a while.

(BTW, does anybody remember how the hell you access the list of saved posts on Less Wrong? EDIT: never mind, here it is.)