You are mistaken in thinking that this happened after the resurrection and that Christ became an omnipresent human spirit co-existing with omnipresence of God.
When the eternal and immutable Spirit of God became incarnate, the Son, because of the incarnation became a quickening Spirit because of he nature of the incarnation and the inseparable fusion of God and man. You are misunderstanding the process. God is immutable and unchanging. God became a genuine man and because of this, the eternal Spirit became associated with the incarnation. A man didn't and can't become God. God became man. This happened at the incarnation. There was never a time when the Son wasn't God manifested in the flesh.
As to the present and future, the life-giving Spirit of Christ is experienced in our lives due to his incarnation and work of redemption that leads to our regeneration and resurrection.
Once I was lost and without God because of the curse from Adam and my own sins, but now Christ has become that life-giving Spirit to me.
Is 1 Cor 15 about the resurrection of Christ?...
35 But some man will say, How are
the dead raised up? and with what body do they come?
36 Thou fool, that which thou sowest
is not quickened, except it die:
37 And that which thou sowest, thou sowest not that body that shall be, but bare grain, it may chance of wheat, or of some other grain:...
42 So also is the
resurrection of the dead. It is sown in corruption; it is
raised in incorruption:
43 It is sown in dishonour; it is
raised in glory: it is sown in weakness; it is
raised in power:
44 It is sown a natural body; it is raised a spiritual body. There is a natural body, and there is a spiritual body.
45 And so it is written, The first man Adam was made a living soul;
the last Adam was made a quickening spirit.
46 Howbeit that was not first which is spiritual, but that which is natural; and
afterward that which is spiritual.
