Raymond, I enjoyed your explanation. Like you, I have done a reconstruction of JW Theology. I agree with you, this passage is literal. The number is also important, because John "saw" the number and "heard" the number (Rev. 7:4; 14:1).
Here's something that you will find interesting. If this is the case and the chapters follow each other in chronological order, then the sealing is to be a future event and the interpretation of JWs is wrong.
"The transition between aforementioned chapters of Revelation [6 & 7] is introduced by the Greek phrase Καὶ μετὰ τοῦτο (Rev. 7:1 Tischendorf’s New Testament, 8th edition; cf. NA28 footnote), “and after this,” “this” referring to the breaking of the sixth seal, specifically the kings of the earth and their followers, finding refuge in their underground shelters (Rev. 6:15-17)."
And as you remarked, the Israel of God must come first. The 144000 is
taken out of the Israel of God (Gal. 6:15, 16). That means the Israel of God
must come together before the great tribulation, or am I wrong to assume that?