The question I was going to include with the above statement was, if transitory joy is potentially pointless in God's eternal purpose, then it seems to follow then that whatever purpose the transitory suffering of Jesus served is also potentially pointless. But you then carve out an exception here, understandable since it's central to your belief system, for transitory suffering.
Regardless, I have always thought that the word 'necessity' really doesn't work well when discussing God, it implies either that God is not omniscient and couldn't think of another way to accomplish the same thing, or that god is not omnipotent and that he is constrained by some type of rules external to him. It simply is not necessary that Jesus suffered and died and was resurrected, God could have easily set up many other ways for eternal life to be realized.
But what it does potentially do is put your god belief on the same level epistemologically as thousands of other fantastic claims that have been made by people who also do not have any proof that will convince anyone else but are convinced nonetheless. I may be wrong, but I would guess that you think a lot of those claims are not actually well supported. I'm not sure why the fact that the proof that has convinced you has not convinced the majority of human beings who exist, many whose internal proof has led them to contradictory conclusions to your own actually, does not then temper your conviction that your proof is valid in the first place.
But the Bible was written and sold as a book that contains the truth, and we are warned in a couple spots I thought to not subject some of its 'truths' to reason which may lead you astray from faith. Regardless, the biblical account of creation was held by a large number (majority?) of Jews and Christians for the vast majority of history to be literally true and factual, and it's not like the major Christian churches responded to the findings of cosmology, geology, and biology that the earth and universe are billions of years old with, 'Oh, thank you for clearing that up for us, you of course are correct and we have been misinterpreting Genesis for millenia obviously'; quite the contrary. Are you surprised that these scientific findings weren't more immediately embraced by Christianity (with full recognition that I'm using that term very generally)? There were a lot of 'reasons' given for not accepting these findings that came straight from non-scientific quotes from a book that does not have much science in it.
To note that the Bible is not a scientific textbook seems to be a little bit of a red herring; I don't think anyone disputes that. The issue seems to more accurately be that believers are instructed to accept (some of, at least) what the Bible says as being the truth, based on whatever foundation, and I'm not aware of many Abrahamic religions that embrace the attitude of, 'you should believe what the bible says about this until science disputes it'.
I'm sure Richard Dawkins could not have put it better himself.