Yes 1914 is critical.
If no 1914, there is no 1918 temple inspection (Jesus cleansing the temple i.e. rejecting all churches 31/2 years after His presence) and there is no 1919 when Jesus found a FDS funnelling truth through the WTBTS and thereupon appointed to act as sole communicator of truth to mankind.
I would stick with the blood issue though. If the doctor says abstain from alcohol, he does not mean that you can't apply alcohol to cuts.
Using blood to sustaining life was not the issue. Eating blood was the issue. Pastor Russell had it right.
It is indeed assumption on the part of the organization to take a dietary regulation, which was a temporary injunction btw (seeing that the other 2 dietary recommendations in Acts 15 were later waived (I Cor. 10:25,27) originally designed to prevent stumbling Jewish members. The moral, as opposed to the dietary injunctions (fornication) was never waived, because it was not temporary.
From there I would go into the extra-biblical breaking down of what is acceptable and not acceptable in terms of blood components. R. Franz has a great chapter on blood issue....demonstrating both the extra-biblical and illogical and lifethreating changes and conclusions of the org on this issue.
Funny how the org's laws prohibit storing blood (no NT evidence to support this) but allow JWs to benefit from the "sinfully" stored blood of others to sustain their lives. Funny also that JWs are allowed to have their own blood drawn and stored in small containers for testing purposes. Where does the Bible define permissible amounts of storage?
Every unique doctrine originated by the Org is in fact extra-biblical
Good luck tonight however you play it.