and remind me again just HOW this miasma of eschatological details has the slightest bit of relevance to whether or not the 1st century Gentile converts have to become Jewish in form and substance to be Christian?
Because as we see in Acts 15:17 as well as Amos there are two groups of people mentioned: "the residue of men" and "the Gentiles who are called by his name". If they had already become ONE, then why are they still TWO.
Actually, we have four as Amos mentions the remnant of Edom, and the heathen. You reference further the residue of men and the Gentiles. MAN this is confusing! Imagine me in my naievete just thinking there were two peoples, Jews and Gentiles, and that EDOM was a pictorial way of describing ALL the heathen, even though other passages (Jeremiah 49) do the same thing. I guess you can tell that I think this hyperliteralism extremely silly.
Simple pictures are best. Amos portrays the judgment of God on Israel, and the returning of God to Israel, raising up the house of David and causing them to rule over the heathen, who are "posessed" by Israel. James comes along and in refutation of the demand that Gentiles become Jews in CUSTOM, says, "The scriptures foretold that God would raise up the fallen house of David and the Gentiles would submit to that house. This is in accordance with what is happening now" thus agreeing with Peter (whom he referenced) and Paul and Barnabas. The "conquering" of the Gentiles is complete under the good King of David's royal line WHO RULES NOW ("he must rule UNTIL he has put all enemies under his feet"). Therefore, there is no need for further incorporation. See? Simple. Straightforward. Internally consistent.
Contrast that with two different groups of people (I didn't even bother to ask who the "residue of men" vs "Gentiles" are and how they compared with the two groups in Amos), absolutely WEIRDO reasoning from James, introducing the concept of a future millenium as reasons why they aren't to be circumcised, mixing the 1st person of Jesus and a first coming not even mentioned with the voice of the Lord in Amos, and just running lines here, there and back to somewhere........, for WHAT? All to avoid the deadly idea that is staring you in the face...., the New Testament interprets figuratively the OT propehcies.
This line of thinking is what moved me FROM dispensationalism. I did a read through of the NT and looked at how IT told me the OT prophecies were to be interpreted. I then went and read Walvoord, Ryrie, Scofield, and others on these verses. Then I read some reformed guys (mostly Calvin and Hendricksen). I found the same scenario over and over and over that we are finding right here. I felt like the reformed guys were looking at the plain obvious meaning of scriptures, while the dispensationalist were playing a game of hermeneutical "twister" to save their theological system. They were pretty pissy about it, too, but to be fair, some of them had been attacked pretty stridently.
All this is just to say that there are TONS of sections of scripture like this in the NT, where the NT "allegorizes" prophecies and demands the right to do so. Can you avoid admitting it? Sure. Others have. But it gets really convoluted sometimes.