1) no sulfite. It inhibits mlf
2) basically let it run it's course but it can be difficult in whites. I would recommend adding a mlf nutrient such as http://www.thegrape.net/browse.cfm/opti ... 12323.html
3) At least several months. You can look for very small bubbles raising up in the wine. If in a carboy the bubbles can be seen in the neck. To make sure mlf is complete, you can test for malic acid with a test such as this http://www.thegrape.net/browse.cfm/accu ... 11914.html
4) Don't try to stop it. Let it finish. If you try and stop it, it could restart after bottling resulting in carbonated wine.