Thank you for your thought out question and kind words!
As far as your first question, the “churned” answer was given here:
As far as your computation on “averages,” it does not mean that 8 x 150 = 1200 so 50 years are missing. The Sakar Murli just relates Brahma Baba’s soul going through the cycle of time as the “model” for explanations. Only Brahma Baba’s life through time has been disclosed with referential points. Brahma Baba takes the full 84 births and when he left his body (1969,) that was his last birth in this “cycle.” Brahma Baba takes 8 births in the Golden age. BUT his second “birth” (name change) is when the Golden age “starts officially.” (When his name changes from Krishna into Narayan 1st -see articles above.) In those 8 births, Brahma Baba could have been 200 years old in one of his births, 145 in another, etc. The word “average” means that we take all values for every birth and add them up and then divide them by 8. That is all. It doesn’t mean that every birth has to be 150 years and also, it does not mean that everyone has to take 8 births of 150 years. Consider Dadi Janki’s age for an “Iron age” average of life expectancy.
Also bear in mind that the “cycle of time” is not a “static line” dividing a circle in 4 equal parts. That is just an easy explanation. The cycle moves continuously without a break and just like you cannot tell when the day starts at dawn, similarly with the ages in the cycle of time. That is the way of Nature, not the way of how an artist would like to paint a picture. 🙂
Consequently, we do not know which “birth number,” Dadi Ji is in or Jagdish bhai. We will start counting again when they experience their first birth after “destruction,” and that could be just like Brahma Baba, before the “official Golden age” or after. That hasn’t been disclosed.
As far as you question of the “advanced party;” the advanced party will allow the “Golden age” to exist. The “Confluence age” is only for Brahmin souls, not for Advance party souls. The confluence age finishes when Brahma Baba takes birth as Krishna. A “new” point to churn is to note that “advanced party” souls are neither in the “confluence age,” nor in the “Iron age.” 🙂
In your last question: Laxmi and Narayan signify Vishu. Also the Sakar Murli, mentions that “Brahma becomes Vishnu,” meaning that Brahma will be a resident of the Golden age.
“Brahma Baba” is the name of a role of a soul. Vishnu is just a mythical name which represents something (sustenance, golden age, the perfect couple, the in-laws, etc) Same with Shankar (destruction, bodiless stage, etc.)