Only in a highly controlling CULT, are you made to feel obligated to explain your reasons to quit a VOLUNTARY POSITION.
I would have handed in my resignation as an Elder, with an "I'm done, and I'm not discussing my reasons. Effective immediately." That would have been the end of it. Saying you have "doubts" is only opening yourself up to a future JC. Should have faked depression and/or being "stumbled" by the new Governing Body Televangelism. Haha!
As for your wife: Sounds like she's royally PISSED because she married a company man, an Elder. Now, you've gone and ruined her "position" (the only one she's allowed to have in this Victorian Era dictatorship) of "Elderette". What's she to do? Walk around like a pee-on, like the rest of the nobodies? Surely you jest!!! But your resignation as Elder will definitely have a silver lining: Wait until the rest of the Elderettes and Pioneer nosey busy bodies start spreading false rumor and gossip about you, AND her, then start treating her like total crap. Oh yes......your wife is about to be shown "Organizational Love", bigtime!! Especially if you start "fading" from the meetings. Then she'll be treated like a leper! This will at first cause her shock, then disbelief, then anger about such abandonment of her conditional so-called "friends." She'll be running back to you, because you'll be all she has left after the spiritual whipping. Think I'm bullshitting? Just wait and see.......her turn at bat hasn't even come yet.