Read up on your own about how long it takes for alcohol to metabolize from the body. How much fat you carry on your body will effect the rate I'd imagine as fat absorbs a lot of toxins as well as the liver. Breast milk is fatty as well, so it may absorb it, but for how long is something you need to find out for yourself unfortunately.
Because our culture is so in love with alcohol, its difficult to get objective information on the effects of alcohol consumption. Your best bet is to research online with independent scientific journals or non-profit resources that specialize in issues related to alcohol and children.
The fact remains that caution should be your bi-word. The infant brain is still in the early development stages and forming important neural and tissue connections. Any negative effects from the environment can have a deleterious effect on that development, thus caution must prevail.
Would it be impossible for you to give up your after dinner wine for the time that you are breastfeeding? Considering the length of your life and the importance of your child's development, you might want to look carefully at the big picture before getting all stressed out about how to control your desire to imbibe.
Sounds like you are going through a lot of trouble for a couple glasses of wine. Is it worth it? Would a few months of abstinence be that difficult? I don't want to sound preachy, but if you feel the "need" to have alcohol every night now, what will you do as the child gets older and things get really stressful? I would suggest that possibly you might want to check yourself -- do without for a while, it will do you good as well as the baby!
BTW -- My mother was an alcoholic and drank lightly throughout all her pregnancies and during nursing. She had numerous miscarriages, had one child very premature who still has some mental disabilities and I have had to suffer with lifelong problems with memory and depression problems that seem to come from nowhere. How do I know it wasn't because of my mother's drinking?
I'd say its not worth the risk.