When Exodus's Pharaoh claimed, according to Biblical tradition, that he did not know "YHWH," it doesn't mean that the Israelites were not worshipping "YHWH."
Unlike Jehovah's Witnesses claim, YHWH is not a proper name in the same sense that humans or angels may have names. In fact, it is an "anti" name.
YHWH or HaShem, as the Jews speak of it, was never recognized as a mundane name. It also doesn't read that way in Hebrew. Jews know this early in life, at least by the time they are old enough for Bar or Bat Mitzvah. Curious that the "translators" of the NWT are ignorant of this being the "non-name" that it is, something you wouldn't be if you know Hebrew or even if you know someone who is Jewish.
In the time of Moses and even before, especially in Mesopotamia, the custom of heathen religions was to use names of deities to get their attention and thus control them (they weren't "Pagans," as that is actually a religion of the people of Europe, like some of the ancient Celtic people--another mistake of the inaccurate JWs; the correct term for a theist who worships gods other than HaShem is "heathen").
All the gods of the heathens therefore had names, in order for the people to get the right deity's attention and thereby have some sort of "control" over them (for a god, once called upon and attentive to such a call by a mortal uttering its name thereby had to fulfill any prayer asked, otherwise it showed itself and its name to be impotent beofore others, mortal and deity alike). The Semitic term for "name" actually means "handle," and the Jewish definition of the term is the basis for the American use of "handle" as a pseudonym for identification when C.B. radio communication was popular in the 1970s (i.e. "What's your handle?" meaning "What is your C.B. user name?").
Because Moses grew up in Pharaoh's court and was also familiar with the worship of the Hebrews, Moses asked God for his "name" or "handle." The reply was not something Moses expected. "I AM WHAT I AM" or "I SHALL PROVE TO BE WHAT I SHALL PROVE TO BE" is what HaShem replied.
In other words, HaShem didn't have a "handle" or "name," not in the mundane sense. God's name was what he proved to be, who HaShem was, by reputation. God was defined by God, not by any mundane name like the gods of Mesopotamia. HaShem doesn't have to respond to those who use his "handle" because YHWH isn't a "handle." It is the definition of God's identification. It means, in modern English terms: "I am defined by myself--who I am and what I do." It is circular reasoning, God proving God by God and no one else's standard.
This is why although Abraham worshipped HaShem, Moses still asked for a name. The Israelites knew of The Name, but since they also spoke the language of The Name, it both meant more than could be defined while at the same time nothing at all.
This is the meaning behind Pharaoh's statement, that he did not know HaShem. In fact, he may not have heard YHWH pronounced at all. It is written down, but the words of Scripture are not necessarily meant to reflect the actual words used in the conversation, as if taken down by a court reporter and thus preserved in that fashion.
No, more than likely Pharaoh heard a substitute because he would not be speaking Hebrew. He would be speaking Egyptian, and Moses and Aaron had to speak in Egyptian instead of making Pharaoh, a god, speak in the lowly tongue of slaves.
And in fact, being that YHWH is an anti-name, what Pharaoh heard from Moses and Aaron would be insulting, regardless of the actual terms used. To paraphrase: "The God of the Hebrews, He-Who-Cannot-Be-Defined-or-Controlled-By-a-Name, calls out to you, Pharaoh, by name, and commands you to let his people go free."
The God who had no handle used Pharaoh's "handle" and was telling him that HaShem could thus control him.
Pharaoh responded: "I--the god--do not know of this He-Who-Cannot-Be-Defined...and therefore cannot be controlled by him who uses my name."
In the Cecil B. DeMile classic, The Ten Commandments, they shorten this definition of God's name to: "He-Who-Has-No-Name." This wasn't an invention or ignorance. It is the real understanding of the people of HaShem and the same conclusion Christians have come to understand through Jesus of Nazareth's teaching.
When Jesus told his followers that they 'should not pray as the heathen do, using word upon word,' he didn't mean that people were not to repeat themselves. If that were true then many of the psalms would never have used in worship as they often repeat themselves over and over again the same way Kingdom Songs sung by Jehovah's Witnesses repeat the chorus or refrain of their songs over and over again. At Matthew 6:7, Jesus said that they shouldn't babble "like the heathen" when praying.
This babbling was not merely repeating, but using "word upon word," meaning in Semitic language "name upon name." In Jesus day there were some who felt they should call upon God by uttering YHWH, using it often in prayers, or by heaping up YHWH along with other titles, like EL, ELOHIM, ADONAI, etc. (sounds a lot like the JWs today who constantly repeat "Jehovah" in their prayers, thinking God will "hear them for their use of many words (names). Heathens still believed in Jesus' day that by uttering lists of names they could control gods and force them to do their bidding, to give to mortals what they wanted. Jesus stated that HaShem did not have such a "handle" and didn't need one. Why? " Do not be like them, because your Father knows what you need before you ask him."--Matthew 6:8.
Your conclusions don't fit either the Hebrew language, the understanding the Jews have had of the text from antiquity, and the basic meaning of names and their importance in heathen worship in contrast to the "nameless" HaShem (YHWH).
I will say it before and I will say it here again: You cannot take the Scriptures out of their context, the religions that wrote them down, and expect to understand them. You need to think and read and believe like those who wrote them to understand the meanings of what is written down.
You are using the Bible the way the JWs do, as if the Bible is the source of the Hebrew's history. It is not. It is not the source of religion but the reflection of a religion. It's not what a religion should be based on, instead the Bible is based on a religion.
Since it is a reflection and not the source of this religion, anyone who reads it independently of it gets the same that anyone else would get if they read a reflection--their understanding of things comes out BACKWARD.