[Maigret]

1. I was always under the impression that the "two towers" were Minas Tirith and Minas Morgul (Ithil), not Isengard and Barad-dûr.

I'm afraid your impression is wrong, I just read the Two Towers and it most definitely is Orthanc and Barad-dur that are referred to.

[Elenya]

it most definitely is Orthanc and Barad-dur that are referred to.

If I'm not mistaken, Tolkien was actually referring to Minas Tirith and Minas Morgul but it's the publisher who took it to be a reference to Orthanc and Barad-dur. And it stayed that way.