"But JWs aren't the only ones who interpret Michael to be Jesus."
There's a small amount of truth in that. I believe I heard (this was decades ago, so my memory may be faulty) a Christadelphian say that Jesus was Michael in some prophetic sense. But they wouldn't have had the same belief as JWs, even though Russell probably got his non-Trinitarian views from the Christadelphians. The Christadelphians don't believe in any pre-existance of Jesus before his conception, while Michael was around before that.
Well, actually, if you Google this topic, you will see that the whole Michael/Jesus thing isn't as unique as some people think it is:
I’ve discussed the fact before that the first Christians believed Jesus was secretly an angel who came down from heaven in the guise of a man (a conclusion with which even Bart Ehrman now concurs). Even if Jesus was a historical person they believed this (a key point in my new book Jesus from Outer Space). And even if semantically you dislike the word “angel” and imagine the first Christians employed some other term for what he was, still they believed he was an eternal being who descended from what they understood to be outer space. And this idea features as well-documented background information in my peer reviewed study On the Historicity of Jesus (index, “angels and angelology,” “Logos,” “Melchizedek,” and of interest to today’s topic, “Michael”). For articles on my blog covering this subject in more focus, see The Original Scriptural Concept of ‘The Lord’ Jesus, Can Paul’s Human Jesus Not Be a Celestial Jesus?, and my two articles on Larry Hurtado’s bizarre attempt to deny this: The Bizarre Fugue of Larry Hurtado and The Difference Between a Historian and an Apologist. Of course the Jehovah’s Witnesses have long claimed to have uncovered the secret truth that, in fact, Jesus was none other than the Archangel Michael, traveling under another name (one that just happens to mean God’s Messianic Savior, suggesting that name, in this case, is fabricated: Christ means Anointed ergo Messiah/Messianic; and Jesus, i.e. Joshua, i.e. Yeshua, means God’s Savior). And there is a good case to be made that they are right. And this case is most expertly laid out in Darrell Hannah’s doctoral dissertation, later revised and published by Moer Siebeck and then Wipf & Stock in 1999: Michael and Christ: Michael Tradition and Angel Christology in Early Christianity.
Was Jesus-Is-Michael an Early Christian Mystery Teaching? • Richard Carrier Blogs
The blood doctrine is totally unique to JWs. . .
Actually, it's not. Many Orthodox Jews have the same doctrine:
FACTS-REL-Judaism-20191106.pdf (defenseculture.mil)
144000 Israelite male virgins referring to Christians of both genders and not being necessarily celibate is unique. The nature of those people is apparently "symbolic", but their number (12×12×1000, extremely symbolic biblical numbers) is apparently absolute.
I haven't looked into this enough to really give an intelligent answer to this subject, however, I would like to ask: Why wouldn't the number 144,000 in Revelation be a symbolic number?