We had a cherry type tomato this year that was watered in Spring when planted to help get it startet but then was totally on it's own and it went wild and even produced Tomatoes until the first frost. (just our normal garden soil, no fertilizer this year and heaps of weeds) It literally thrived even through the biggest summerheat and a dry spell of almost 8 weeks. 2 weeks of which we had almost constantly 39°C from 10a.m. to 5p.m.I was scraping by on rainwater for a while and mostly growing drought tolerant things in the winter when the ground naturally has moisture but recently i set up some gravity fed water from a dam which seems to be doing well. I was eating a lot of stew with homegrown sheep, pigs or chooks, plus what ever else i could find or grow. Since i have water now i'm aiming to grow as much as possible this summer and eating a lot more vegetables and fruit but its hard to sustain your body weight on just that alone especially when working physically. A lot of survivalist types comment that you really need to regularly eat a good amount of fatty meat in order to sustain body weight when eating only natural foods and i would definitely agree with that. In saying that out of the plant based foods i think the tuber crops are the most sustaining. I also like grapes with seeds as i find i can sustain myself on them for a fair while as the seeds have a good amount of fat and protein. This is a common theme, most things that you eat the seeds with seem to be more sustaining.
There is (not the one we had) a wild-type Cherrytomato heirloom which is called "post office spoonfull". I've learned, that because it's very close related to the wild growing tomato types from Peru, it's especially hardy and resillient. No pruning needed and produces a ton of fruits... maybe that would be a variety for your place to try? Tomato roots can grow down about 2m very easily some even deeper, maybe they are hardy enough to grow in your area with a little help
