This is a great list, havard!
Seems like the Pick a Path / Fantasy Forest book #9 (Jason's First Quest) could be set in Milenia (in the Hollow World). The locations in the book might be very specific, though, if they are implicitely set in the RW Greece (though mythic). That would take a little more converting.
That's kind of funny that only one specific book was implicitly set in a Mystara setting -- (Super Endless Quest #15, The Vanishing City.
It seems like the title immediately under that one, (#18) Prince of Thieves, could possibly be set in the thieve's capital of the Norwld, i.e., Landfall. But if it has some made up city/town locations in the novel itself then that would be harder to "ret-con."
As for many of the other D&D books, I'm okay with having adventures set in other lands, or dimensions that the characters could occasionally visit, in my campaign.
As a matter of fact, if I had occasion to just conveniently place some kingdom or reference from certain books into other places from other worlds, Laterre could possibly be used.
lastly, I have a few kingdoms around the Sylvan Realm region. The Thunder Rift setting implies there are other countries around Thunder Rift, and decided that that secluded valley and its nearby (mostly-)human kingdoms would be around the Sylvan Realms. So, I could place a few other realms there, too, from the books. Those are just my ideas. Without lots of additional time, it wouldn't be something I'd pursue, but it could be fun. I do like picking up every little tidbit of canon that can be used in shoehorning D&D into the Known World and Mystara setting.