Socrates:
Part of the problem may be the premise you are working under. You are equating:
"when [Stephen] cried out for Jesus to accept his spirit"
with
"an obvious reference to an instant resurrection to Jesus in heaven."
Consider another possibility. When Jesus was about to die, here is what he said (or was said about him):
(Matthew 27:50 NWT) . . .Again Jesus cried out with a loud voice, and yielded up [his] spirit.
(Mark 15:37 NWT) But Jesus let out a loud cry and expired. ("Expired" is ekpneo; Strong's #1606; literally "breathed out")
(Luke 23:46 NWT) And Jesus called with a loud voice and said: "Father, into your hands I entrust my spirit." When he had said this, he expired. (Expired = same as Mark 15:37)
(John 19:30 NWT) When, now, he had received the sour wine, Jesus said: "It has been accomplished!" and, bowing his head, he delivered up [his] spirit.
(Alternate renderings are linked to the citations.)
Compare these words with Stephen's:
(Acts 7:59, 60 NWT) . . .And they went on casting stones at Stephen as he made appeal and said: "Lord Jesus, receive my spirit." 60 Then, bending his knees, he cried out with a strong voice: "Jehovah, do not charge this sin against them." And after saying this he fell asleep [in death].
Acts 7:59, 60 ESV) And as they were stoning Stephen, he called out, "Lord Jesus, receive my spirit." 60 And falling to his knees he cried out with a loud voice, "Lord, do not hold this sin against them." And when he had said this, he fell asleep.
Some time before Jesus died, he said:
(Matthew 17:23 NWT) and they will kill him, and the third day he will be raised up." Consequently they were very much grieved.
(Matthew 20:19 NWT) . . .and will deliver him up to [men of] the nations to make fun of and to scourge and to impale, and the third day he will be raised up.. . .
(Mark 8:31 NWT) Also, he started teaching them that the Son of man must undergo many sufferings and be rejected by the older men and the chief priests and the scribes and be killed, and rise three days later.
(Luke 9:22 NWT) but said: "The Son of man must undergo many sufferings and be rejected by the older men and chief priests and scribes, and be killed, and on the third day be raised up."
(Jesus maintained that he would be 'raised up' on or after the third day.)
And after Jesus returned to life, but before going up to heaven, he said:
(Luke 24:46 NWT) and he said to them: "In this way it is written that the Christ would suffer and rise from among the dead on the third day,
(Jesus is still holding to the idea that he was raised on the third day.)
And some years after his death Paul said:
(1 Corinthians 15:4 NWT) and that he was buried, yes, that he has been raised up the third day according to the Scriptures;
(Paul is holding also to a third day resurrection.)
Take Care