Let me ask a couple of questions: "I have not the slightest doubt that they know they have misunderstood the blood issue". From what I read on your other post, I agree they're wrong, even from a scriptural point of view. But what makes you think they know they're wrong?
The position used to be simple. No blood - no compromise. If you die you will get resurrected. Simple. If they still believed it nothing would have changed. Instead they are doing everything in their power to compromise with bullshit about factions - even hemoglobin THE definitive faction. HLCs main job is to persuade JWs to accept every treatment that can possibly be justified. It is a damage limitation exercise. They would only do that if they had lost faith in their own dogma but would rather let people die than admit their error.
What makes you think they know that Jerusalem was not destroyed in 607 B.C?
The historical evidence is 100% against it and literally 0% in favour. We know that they understand the issue because of Carl Johanson's work and Ray Franz's revelations.
Regarding the UN, what were the real reasons, in your opinion? I've read about the subject, but I haven't read anything claiming they had hidden reasons.
Their motives are opaque but it is possible that they cosied up to the UN to gain political capital in countries where they are restricted. They even praised the UN in WT articles in direct contradiction to previous attacks on the UN. They allowed elders in Mexico to join the military reserve because if they admitted to being a religion rather than an educational charity they would lose real estate.