First, I agree with @InLogicWeTrust. Secondly, try a butterfly garden. You'll get flowers and butterflies. My thumb is green, but goes through black moments.
Kale is a hardy plant. It survives heat and cold. The ornamental varities are beautiful.
also i was thinking since you said you have full sun. perhaps the hostas got too hot, you could try them again but make sure you plant them somewhere the can get shade for the hottest part of the day. oh, and now they have created a few that do better in the sun so you could look into that as well
@PeppermintDreads ooh! i just thought, have you tried covering your plants with mulch in the winter? a 2 inch layer can make a huge difference. and i never paid for it, i just take all my stuff from the garden thats dead or whatever and make a compost pile. i just us the stuff that hasnt degraded all the way yet. and whats left is great for mixing in the dirt at the start of the next spring for added nutrients..
i live in washington, so some of these may not work for you, but here is a list of a few things i planted 5 years ago and havent touched since, they are flourishing to this day. shamrock, cyclamin, lewisia, colombine, foxglove, mint, yarrow, bluebells, crocus, lilac, indian soap bush, trilium, and so many suculents i can't name them all, but some do good with cold and others dont, you have to make sure you get ones that come from regions that while still dry, tend to have cold nights. i hope some of these work for you!
@PeppermintDreads try to stay away from things like lillies then. thats death to kitties. there are a few things that are safe but effective at keeping critters away. my grandma sprinkles finely ground pepper near her plants. critters smell it from a ways off and are generally smart enough to leave it alone. also i heard green apple extract is good against dogs, but i havent actually tried it. also i planted a special patch for my critters that had things like catnip, carrots, strawberries. things that critters love. the cat was easy, because it loved the catnip and didnt care about the rest of the plants after it had that. the dog took a bit more training, but she learned pretty fast that she was allowed to eat and dig there, but the rest was off limits. you could try something like that.