SH:
The issue here is that we are not dealing with Yaakov Avinu. The idea of “Lo Mes” is something unique to Yaakov, and was never hinted to for anyone else since creation of the world (with the exception of those that the gemora says never experienced misa). So the “alive” myth is completely unacceptable, as per Torah and as per logic. To believe that is complete hergesh. I am uninterested in the efforts to provide afterthought logic to rationalize this.
As for the being oveir an issur, this is the expression used by several of the poskim who dealt with the Kever Rochel shailoh. They did not conclude that it is better not to, but that the issur is clear and cannot be subjected to compromise.
I cannot speak for the Chid”a or other poskim from the Sephardic world. It is known that many of their piskei halacha differ from the Ashkenazic prevailing halacha. I have an issue with someone who concocts his own heter for something, and then tries to justify it with a basis from poskim who paskened their halachos for their own communities. These same Sephardic communities were not under the jurisdiction of Rabbenu Gershom, and technically did not accept the takana against marrying more than one wife. With the greatest of regard for the Chid”a, this is a case of apples and oranges.