Dearest Headspinning, peace to you! I am compelled by my Lord to comment here, so please allow me to respond. Thank you!
A lot of folks here respond to questions like yours with practical comments. And there is nothing wrong with that: if facts show that what others tend to state the Bible teaches is not what it teaches, then you should know about that so that you can draw your own conclusions (if you cannot hear Christ, the Holy Spirit, on the matter). But for those who realize that religion (and particularly the WTBTS) is not what it purports to be... but still wish to understand God's will... there is another way to look at this issue and that is NOT through the Bible but through the eyes and mind of Christ.
Christ fulfilled the Law Covenant, dear one so he had to be fully aware of it and its provisions, including the sanctity of blood. According to the Most Holy One of Israel, JAH of Armies (who you may still know as "Jehovah") the life... is in the blood. One's life force... or spirit... is contained in one's blood. It is how one's blood speaks (as did Abel's). Thus, one's blood is one's life. Spill too much of it and one's life runs out. Same with animals and plants (sap).
Christ is recorded to say, however, that no one has greater love... than to give his life... on behalf of his friends. And he gave HIS life... the most important part of which included his BLOOD. Given than, then, how can it ever be WRONG... to give one's BLOOD... one's LIFE... on behalf of one's friend(s)? If that is true, how then could it be wrong to give one's blood on behalf of, say, one's child, or parent, or sibling, or spouse? Aren't those one's friends, indeed, one's brothers? What about one's neighbors? Isn't one to love his neighbor as himself? And what of strangers?
Christ is recorded to go farther than that, though, for he said that if we are to PROVE ourselves sons of our heavenly Father we must also love... our enemies.
If, then, there is no greater love than to give one's life... and the life is in the blood... and we are to love even our enemies... where is the basis to WITHHOLD our blood, our LIFE... from another... even an enemy... if that one needs it to live?
The WTBTS falsely teaches such withholding on the basis of one being "disobedient" and a resultant prospect of destruction for such disobedience. This is a lie. How so? Because either way, whether one gives one's blood in order to grant [temporary] life to another... or whether one exchanges his/her life as a result of any "disobedience"... one has shown GREAT LOVE in doing so. And... there is NO LAW against love. So, there can be no judgment... or condemnation... for such an act... because there is no law against it because it is an act of love!
The fulfillment of the Law isn't restricted to not trangressing it. It includes SURPASSING it... with love... by means of mercy. If YOUR life or your loved one's life depended upon the blood of another... you would want that other one to give his/her blood so that you or your loved one could live. All things, then, that you want men to do to YOU... you must do... or give... for them.
Knowing what God requires of us is NOT unknowalbe, mysterious, or rocket science. We only need to look to Christ, who not only GAVE his blood on behalf of the world... but TOLD us to DRINK it. True, we don't do so literally, but neither do we when we take another's blood into our bodies via IV means.
The directive handed down by James (pursuant to what he received from the Holy Spirit) had to so with the practices of the nations that the apostles and disciples were now sharing the good news about Christ with. These had a practice of eating foods sacrificed to idols, things strangled, and drinking (literally from a cup) blood. This latter they did with things like the blood of their enemies... or that of animals... because they, too, knew that the life of a being was in its blood. Thus, they believed that by drinking the blood, they would literally take the life... and particularly the attributes (i.e., physical strength, natural abilities - for example, eyesight of an eagle, etc. - wisdom, intelligence, psychic and other abilities)... of the blood's provider into their own bodies. They didn't do it to live but to "take" the provider's "strengths". Of course, they killed the provider first, solely for the purpose of GETTING such blood. This was a blatant disrespect for the SANCTITY of that provider's blood... and life.
But there is no law against love, dear one. And giving your blood so that another can live... if you can, for not all can... is a demonstration of great love. However, your own conscience must understand this - it cannot be because another compels or "guilts" you into it, anymore than another should compel or guilt you out of it.
I hope this helps... and sets your mind... and heart... at peace on this matter.
Again, peace to you!
A slave of Christ,
SA