Doubtful you can save it from the point it's at now.
If you had it indoors, that was one strike against it, as junipers are strictly outdoor plants - even in your area. Another strike against it was the heavy Miracle Gro feedings. Bonsai are very sensitive to heavy frequent fertilizing, & when fed it should be a urea-free product meant for bonsai.
If you do lose this tree, but wish to try bonsai again, do some reading/research up first to help make it a better experience for you. Don't feel too badly - we all have learn from experience.
My body is a temple. Unfortunately, it's a fixer-upper.