Well I would base your decision about what to do on how your wife will react. I presume you would prefer she left the org. So I think your pressure point is where Listener pointed you. But I wouldn't demand some headship thing. Just talk to her. Insurance... sure it is a valid point, but how will it be received by your wife. I am thinking it would be unnecessarily confrontational. Feels good, but produces the opposite effect.
You are her husband, not some jagoff elder or some phony baloney publishing company. So maybe say to her that you feel you should be the designated health representative. Maybe even agree to honor her wishes. Then go through the excruciating details with her. What a GOLDEN opportunity to indirectly point out the absurdities of the blood doctrine. SINCERELY ask her to decide all the silly questions about fractions. It will drive her batshit, and you are the good guy "just trying to follow the org". Jiu-jitsu my friend. All about taking someones energy, and redirecting. Never oppose force with force. If she agrees, she could just tell elder jagoff 1 and 2 that she needs to redo the card.
Yeah, I really think I would need more backstory on your wife to help craft an appropriate response. How dedicated of a JW? How long has she been in? Born in, joined as an adult? How well does she handle you not being a dub. How well do you two get along regarding JW?
If she doesn't trust you, then that is always your step 1. The enemy for both of you is not in your home. It is outside.
-Matt