I make primarily 3 Gallon batches in a 5 gallon kettle and I have no DMS issues that I can detect.
I don't find that DMS is much of an issue unless I'm brewing with Pilsner Malt. Then I can really smell the DMS escaping during the boil, but I've never had DMS problems with Pilsner Malt beers, either.
It's going to be hard for you to keep the boil-off to 1/2 gallon, from my experience, which means you'll end up boiling off a higher percentage of the wort with small batches. That should further decrease DMS. Even at 0.5 gallons of evaporation, you'd be above the 8-15% evaporation recommended for DMS removal.