Yitayningwut,
The things called “erva” in the passuk are absolute, otherwise there’s no reason for the Gemara to point to them. Everything would be talui in minhag hamakom.
The Ria”z is not saying pshat in the gemara per se, he’s saying what the halachic nafka minas are.
You wrote earlier that there’s a chilluk between issur v’heter and the momonus of the kesuvah. You’re wrong, though, because there’s no explicit contract on das Yehudis; things which are assur (tznius related or if she’s machshil him) cause her to lose her kesuvah.