I cant offer much help with the tomatoes, but growing sweet corn is similar to growing field corn.
Sweet corn works fine on 30" rows but works best at very low populations to facilitate larger ears. We plant ours around 19,000. Unless you are into the organic farming I would suggest an in furrow insecticide and also planting a super sweet variety such as offered by Seminis (my personal favorite is called "passion"). Some Semis varities are resistant to ear worm which will make a substantial difference at the roadside stand. Seminis now even offers a RR variety which could help with weed control.
Also be aware that not all field corn herbicides are safe for sweet corn. Read your labels. You can still use Atrazine with acetechlor for your pre-emergent and you can follow up with Callisto if you still have weed issues.