Hi, You have raised some interesting points that become entangled with both theology and Greek grammar, and how one untangles this is the product of interpretive problems. Let's take your Scripture citations seperately:
1 As far as 1P3:18 is concerned the problem is that we do not have the word "in" [Greek EN] occuring at this text. as a look at the KIT will show, the text has the word Pneuma" [Spirit] in a particular grammatical form called the "Dative" construction.This construction allows the word "Pneuma" to be written as "Pneuma-ti" and then there follows the tangle of trying to translate this one word. In English the Dative construction can be expressed with the use of four seperate words called "modal auxillaries" These four are: "in" "by" "for" or "to" so in this case at this text we have four possibilities: "in the Spirit" "by the Spirit" "for the Spirit" and "to the Spirit" [Don't let the presence of the article distract you. The dative always implies the article For instance "ev Arche" in Greek is most naturally expressed as "In the Beginninig in English]
Since the word "to" suggests an indirect object, almost all translators reject the translation of "to the Spirit" here, this despite the KIT insisting on using "to" in the interlinear. Since "for" suggests a reflexive action, that too is almost universally rejected.
This leaves us with the two options of "by" and "in" So which is the correct usage here? Translators are almost equally divided, although a larger percentage favour the latter. The KJV, NIV NKJV and even one once published by the WTS, the Emphatic Diaglott says "by". In fact the NWT has itself translated "Pneumati" with "By" at Mar 2:8, so they can hardly complain if someone does so here. If "by" is the preferred translation, then the meaning is clear: That the Holy Spirit, as God, raised Jesus from the dead. Naturally, the WTS leadership would rather have their most precious limbs torn away, than bend the knee to that concept.
So they stick with the alternative. But no one would be so reckless as to state that the dative construction can be rendered with "As" hence implying that Christ was resurrected "AS" a spirit. As you have shown, being "In the spirit", like being "In love" does not negate the idea of physicalality. The WT leadership state that had Jesus taken up His body of flesh and blood, then this would have negated His ransom, since He is taking something back, that He had already given. This can easily be refuted in at least two ways: He also ransomed us with His life, not just His blood, so had Jesus taken His life back as well, that too, would negate the ransom. Another point is that it appears that Jesus did not take His blood back. When He was crucified, He spilled His blood for us, and that indicates that it fulfilled its purpose. When He was resurrected, there is no indication that His resurrected body had blood in it. We know His new body contained "flesh" and "bones" [Lu 24:39] Now, 1P3:18, indicates that there was a third elrment in the resurrection body, and that is "spirit" To use an illustration, If you cut Jesus' skin before He died, the element that would have poured out would have been blood, but now with the Resurrection body, if you happened, theoretically, to cut His skin, the element that would pour out will be "spirit". It is this element that makes the Resurrection body such a marvellous intrument.
It is trans dimensional in that it exists outside the restraints of physical laws. Jesus appeared in a closed room. He did'nt "walk" through walls, as the WTS leadership so ignorantly claims. He just existed there. He chose to appear and then chose to disappear. In the Assension, He lifted away from the sight of His disciples, and then He was in heaven. He did not "travel" there. He just was. It is this marvellous body that can exist in heaven as well. It is a body of "flesh" "bones" and "spirit" and you know what? Paul tells us that that body is one that is promised to all believers. Not just an ignorant 144k! [Phi 3:21]
This new kind of body, of which we know nothing, is called a "glorious" body by the NWT translator, "Body of glory" by others like NASV It is what awaits believers. Imagine a body that can hear in a transdimensioal state, that can see clours far beyond the physical spectrum!
This is what the NWS leadership is robbing their followers of.
2 Now in the light of the above, yes - there is a sense in which Jesus is a spirit. But that is not all He is. The entire context of 1Cor 15 is talking about the resurrection of the body. The WTS leadership disputes this because the word "body" is not mentioned in the section of vss 42 - 58. Well,actually it is, but in a different way. For instance, 1Cor 15:53 says "That which is mortal must take on immortality" What is "That which is mortal"? Ro 8:11 refers this to the BODY. The Bible nowhere talks about resurrected " ghosts" or even "spirits" So the resurrection that Jesus experienced was that mentioned in 1Cor 15. His "mortal" body [it was "mortal" since it could be killed] took on immortality, and the process that allowed that was that He was imbued with "spirit" . Being the first to taste of this phenomenon, He became "life giving" also to us. So, being a "life giving" spirit, did not inhibit His being flesh as well.
It is this resurrected body that will be seen again when He returns, in visible form.
It is this body that all believers will enjoy throughout all eternity. They will exist on earth, if need be, as well in the most Holy of heaven, and anywhere in all spatial creation. Christ promises nothing less for all who believe.
Cheers