I still think there needs to be resolution of your interpretation of Paul with the other inspired authors Matthew, Mark and Luke.
In 1 Thessalonians 4:15, Paul is speaking of the end times, where the resurrection of the dead is closely associated with Christ’s Parousia. So therefore, Paul is speaking of those who have died physically, but will have their body resurrected. Their soul may already be in Heaven, but is certainly alive… as affirmed by Matthew22:32, Mark12:27 and Luke 20:38 which all say that God is the God of the living not the dead.
To expand the context a little, as Jesus was rebutting the Sadducees who said there was no resurrection, Mark 12:26-27: “26 And as concerning the dead that they rise again, have you not read in the book of Moses, how in the bush God spoke to him, saying: I am the God of Abraham, and the God of Isaac, and the God of Jacob? 27 He is not the God of the dead, but of the living. You therefore do greatly err.”
Are the spirits not alive in heaven and aware of what is going on? Let’s please go back to Luke, this time in Luke 15:7-10: “7 **I say to you, that even so there shall be joy in heaven upon one sinner that doth penance, more than upon ninety-nine just who need not penance. **8 Or what woman having ten groats; if she lose one groat, doth not light a candle, and sweep the house, and seek diligently until she find it? 9 And when she hath found it, call together her friends and neighbours, saying: Rejoice with me, because I have found the groat which I had lost. 10 So I say to you, there shall be joy before the angels of God upon one sinner doing penance.”
Before the Resurrection, the physical body may be dead, and the spirit is alive. The spirits in heaven are aware of what we do on earth. The living saints on earth and in heaven are quite simply one family in Christ.