Did Paul change his mind concerning Jesus as the Son of God, or did God the Father through Jesus the Son call Paul out of unbelief unto belief for PURPOSE?
Did Paul become a recipient of the first-fruit of the Spirit? Why is there a first-fruit of the Spirit? 
Joe 2:28
And it shall come to pass
 afterward, 
that I will pour out my spirit upon 
all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions:
All flesh today or just the Paul's for purpose? When is 
afterward ? Can just anyone that free willing wants to receive the Spirit of Truth or just the ones God is calling for purpose?
Acts 22:9 And they that were with me saw indeed the light, and were afraid; 
but they heard not the voice of him that spake to me.
Gal 3:2 YLT this only do I wish to learn from you -- by works of law the Spirit did ye receive, 
or by the hearing of faith? [or 
out of hearing of faith]
Gal 3:14 YLT that to the nations the blessing of Abraham may come in Christ Jesus, 
that the promise of the Spirit we may receive through the faith. --- What is, "the faith," the called hear, out of which they receive the Spirit? Is it not the obedient  death and thus resurrection of Jesus the Christ.
Jesus on the cross became the, obedience of faith. 
IMHO
Eph 2:8 [to the] for [to] grace ye are having been saved, through [the] faith [obedient death], and this not of you -- of God the gift,
You have been saved, because of, the obedient death and thus the resurrection of Jesus [grace of life]
Heirs (not yet  inheritors) of the grace of life. As in 1 Peter 3:7