If you use a wood burning stove you can use the ashes from it or anywhere you can get ashes and spread it on the potato plants and the bugs wont like it
From my expierience you cannot go wrong with heirloom tomatoes the ones I suggest would be Cherokee Black, Cherokee Purple, and Ponderosa Pink these can be found in the Totally Tomatoes Seed Book. For Sweet Corn I recomend the Serendipity variety and I think can be found in the Gurney's seed...