Text overlapping in kdp

What your research should have told you is not to try to specify a font for ebooks. 🙂

Seriously, ebooks of all kinds are best left with generic font definitions so that the reader (app or device) has maximum flexibility to apply its own font control, as adjusted by the user. To try and specify fonts only accomplishes three things, all bad: it bloats the file size (which can cost you as a seller); it often produces problems with a clean presentation, even if you "fix" the problem you first see (as the reader keeps "fighting" to use its own styles and settings); and it's against the nature of the medium, which is to give the reader a flexible, adaptable book that will be displayed to them in an optimized way.

Redo your book with simple, generic fonts such as Calibri and Cambria, or Arial and Times New Roman, and do not embed fonts in the file. Let the Kindle reader handle the presentation. The pairing of serif and sans-serif, each in four faces (regular, italic, bold and bold-italic) should be all the styling your book needs.

Producing Refllowable ePubs is not intuitive. For example, no page sizes as such, you need to use Paragraph (and Character) Styles, best not to justify text, images need to be anchored, no folios, the reader can change the font and size, Master/Parent page content is not implemented and a knowledge of HTML and CSS can be helpful.
LinkedIn Learning have an excellent tutorial you might consider taking: "InDesign CC to EPUB" by Anne-Marie Concepción (you can get 30-days free access).