תניא נמי הכי המדיר את אשתו שלא תשאל ושלא תשאיל נפה וכברה ריחים ותנור יוציא ויתן כתובה מפני שמשיאה שם רע בשכינותיה
Someone who imposes a vow on his wife that she may not borrow or lend her kitchen utensils like sieve, mill, oven etc. must divorce his wife and pay her Kesuba because he makes a bad name for his wife among her neighbours
Well, you seam to have a misunderstanding of the Ramba"m. Loving someone and respecting someone are two different concepts. Even being respect a natural consequence of love, one may respect someone without loving him.
That said, you have the obligation to love your wife like yourself and every other Jew, and the obligation to respect your wife more than you (...
Because Judaism allowed a man to have more than one wife, until a thousand years ago, technically a married man could go find another woman without breaking halacha, and thus the strictest halachic definition of "adultery" only concerns relations between a married woman and a man who's not her husband.
Still, it should go without saying that for a married ...
Some sources to support @Mbloch's answer to understand the Sugya in full (Gemmorah Avodah Zara 36a).
In short, it is a [very severe] Rabbinical decree, since Rabbis compared all gentile women to ritually unclean (נידה) it can be [speculated] as adultery Derabanan. All other comparisons (mistress, gentile or prostitute) do not constitute adultery:
Adultery, or Arayot in Hebrew, in Jewish law is (according to yeshiva.co here)
the prohibited sexual relations a man or woman, married or not,
can't have. The list appears in Torah, Vayikra 18 and 20. All those
listed, will be punished with "Karet" and in addition, some carry the
death penalty by Beth Din as well.
The prohibition is not only on ...