I am pretty "out" in my atheism. I have had a lot of conversations about religion from people of all beliefs. I also hate the tithing system. It seems to hurt so many people who really can't afford it.
Unfortunately, a lot of Christian churches are preaching "prosperity" gospel. The idea is if you give a lot of money to the Church, God will reward you with even more money. Of course, it doesn't work out and people who are having a hard financial crisis are worse off. I did find a good article
on how well the churches are making out and how hypocritical they are being with this prosperity gospel. The article is focused on the question on whether the church should be taxed like any other business or not.
I have found that becoming less fundamental is a slow process. I would suggest friendly conversations with your wife, but don't be afraid to bring up some tough issues.
For example, I was talking to a neighbor about gay marriage. He said that he wanted to follow a Biblical definition of marriage. So I started to quote all the other Biblical marriage laws like forcing a raped woman to marry her rapist or killing non-virgin brides in front of her parents.
Most religious stories and rules have very bad logical outcomes if you think about them fully. One example came from a Catholic friend. In school, he was told by a nun that a remarried man is committing adultery if the first wife is still alive. If the man dies in this state, he goes to hell because he is in a constant state of sin. He could ask for forgiveness, but because he is still remarried, he is instantly in a state of sin again. So my friend asked, "If the man kills his wife, he can ask forgiveness and go to heaven." The nun admitted that it would work, but said it shouldn't be done. (Dogma says one thing, but most people tend to go with values they were brought up with instead.)
I would suggest going to some atheist blogs. Lots of people deal with this stuff. My two favorites are Daylight Atheism
From the people who have converted from theism to atheism, most have done so from getting more education. The "God Delusion" is a good book for people on the fence. However, it may help those who are becoming less dogmatic.