Note that this is from memory but, for example, the author of the linked blog
posts makes an outrageous distinction between the free people of "Sparta", which
he calls "Spartiates" and all "Spartans" which includes the helots. This is were
your expression "3% of the population (spartiates)" comes from.
That is an outrageous distinction that is not found in any ancient or modern
source. It appears to be something that the author completely made up in order
to support his revisionist interpretation of the history of ancient Sparta.
First, there is no way to make a distinction between "Spartan" and "Spartiate"
in the Greek language. In Greek, ancient and modern, a person who lives in, or
is from, a place called "Sparta" is a "Σπαρτιάτης", i.e. "Spartiate".
"Σπαρτιάτης" is most commonly latinised as "Spartan", sometimes as "Spartiate",
but there is no semantic difference between the two.
Second, there is no modern source I'm aware of, other than the linked series of
blog posts, and certainly no ancient source that refers to the helots as
"Spartans", "Spartiates", "Lacedaemons", or anything else but "helots", or
simply the slaves of the Spartans. This is because ancient authors only ever
refer to helots when they want to point out how cruel were the Spartans (which
obviously must exclude the helots themselves from the group of "Spartans") and
don't really care about them, or their fate, otherwise. So the idea that the
population of "Sparta" was mostly made up of slaves is a figment of the author's
imagination.
It is true that the slaves of the Spartans were (many) more than the Spartans,
but this is also true of most other Greek city-states, where manual labor was
performed by slaves and many citizens owned more than one slave. In fact, other
Greeks did not treat their own slaves with any less cruelty than the Spartans.
For example, the main source of richess of classical Athens was the silver mined
from the mines of Lavrion where thousands of slaves, including children, were
made to work in conditions that we would, today, rightly find revolting.
From memory again, there were other errors, all of which were the result of the
author trying to play up historical themes for clicks, but I would have to
re-read the series of posts to remember. In any case my recommendation is to
turn to primary sources if one is interested in the history of Sparta. Read
Thucydides, read Plutarch, read Xenophon, read Plato, read Aristotle, read
Herodotus even, but keep in mind that everyone who wrote about Sparta had a
political affiliation, either to Sparta, or to the enemies of Sparta, and in any
case ancient historians were not always 100% accurate.