Is it permissible to recite the morning and evening adhkar in one sitting, and what is the guidance regarding Juwayriyah’s act (may Allah be pleased with her) and Sheikh Al-Islam’s saying, "This is my breakfast, and if I don't eat, my strength will wane"?

There is no evidence that prevents reciting the morning and evening adhkar (remembrances) in one sitting, and the evidence proves the contrary. The prohibition is only if gathering to recite them becomes a habit and a Sunnah. It is not permissible to use this as an argument for the permissibility of innovated dhikr.