I see the events something like this chronologically: 3.5 year tribulation. Followed by “rapture” (Revelation 7, after the sealing of the 144k). Followed by 3.5 year wrath of God on whoever is left other than the 144k.
So who are the living believers that are transformed at the same time as the dead Christians at the 1st resurrection, if they have all been raptured 3.5 years before?