CC, my hubby is an elder and he 'stepped down' for a while, though we didn't know for how long. He got together with me to work out the letter together. He was like you and had become exhausted and our marriage was suffering too. We decided that it was in the best interests of our relationship that he had to do it. He used scriptures to show how marriage and family was important, that the jobs he had to do was taking away time we could spend together. How the wife and children come before the congregation. His resignation was accepted (with reluctance) but he was firm with his decision. Could you do the same? Sit down with your wife and discuss how you need to word it, if she can have some imput I'm sure it will have a good effect.
All the best!!