As has been said, it depends on where in Hawai’i you live. Kamuela on the Big Island is not hot - I curse every time I go there and forget to bring a jacket.
Cost of living, though - well, that’s an issue everywhere, depending on what you want to buy. I find living here fairly cheap, because there is no heat, no need for fancy clothes, and recreation is free if you love outdoor activities. Plus we mostly eat local, and we grow a lot of our own veggies.
But overall, cost of living is pretty bad, and if you want to travel, almost everything requires flying. So, not for everyone.
How long does a breadfruit tree take to mature? That’ll give you a steady supply of calories right there. 
Google says 3-5 years, so the tree we planted (which is indeed growing very well) is probably only 2-3 years from starting to produce.
Meanwhile, sweet potatoes and taro can easily substitute as a ready source of calories. Though I actually don’t harvest the potatoes from my sweet potato patch, as I use the leaves like spinach. I usually have 5-10 lbs in my freezer at any given time.
Taro cultivation takes more attention and you have to be sure to get the variety that works with your land (there is a dry-land taro variety but otherwise it likes to be in a swamp). - I don’t grow it (except for one plant we’ve got just for the heck of it). But it’s certainly doable and lots of people have taro patches. It was a staple crop before people started relying on imports like rice.
Also note that Taro is toxic and needs to be processed before consumption.
(I’m not in Hawaii but I considered trying to grow some, then abandoned the idea when I realized that you can’t just peel and cook it like a potato.)
List of plants and animals common to the Austronesian territories (like Hawaii): Domesticated plants and animals of Austronesia - Wikipedia
Yes you can! Like a potato, you can’t eat it raw, but that’s no big deal. I don’t know where you read that taro is toxic, but edible taro (there are many kinds of inedible taro, including decorative taro and elephant taro plants) is … well, edible.
On the other hand, taro leaves contain oxalic crystals so they are a bit of a pain to use. They need to be boiled in several changes of water until enough of the crystals are washed away that the leaves don’t create an itchy sensation in the back of the throat. I like the taste of the leaves, but even if I had a supply of them (they don’t seem to be particularly available for sale here) I doubt I’d bother any more.
ETA: one problem with taro is that it is pretty bland and gluey, especially when cooked traditional Pacific Islander style. The recipes I use tend to pack a flavor punch by adding spices, lemon juice, salt, and so on.