Neither Amos 9 (which I quoted) nor Acts 15 (also quoted) reads that way. You are placing the cart before the futurist horse.
Here I'll make it easy for you. What happens before the words: "After this I will return ...". Just read the words in bold below:
"Simeon hath declared how God at the first did visit the Gentiles, to take out of them a people for his name. And to this agree the words of the prophets, as it is written; After this I will return, and will build again the tabernacle of David, which is fallen down; and I will build again the ruins thereof, and I will set it up: That the residue of men might seek after the Lord, and all the Gentiles, upon whom my name is called, saith the Lord, who doeth all these things." [Acts 15]
Now what happens after "After this I will return ...". Just read the above words underlined.
Please note that the "Gentiles upon whom my name is called" is the result of the "visit to the Gentiles [starting at the House of Cornelius] in order to take out of them a people for his name". The visitation comes first and note that the Gentiles after His return are already called by His name --the end result of the visitation.