I'm so sorry for what you're going through! The same thing happened to me after I got highlights. Having your hair so damaged is bad enough, but having to cut so much length off is really adding insult to injury.
There are lots of great deep treatments. You might want to type "deep treatments" in the search bar and see what comes up. Personally, I would look for a hair mask, or any deep conditioner that's meant to be left on for like a half hour or so. ( Not your usual after-wash kind) Go for moisture right now, not protein. Your hair's too vulnerable right now to experiment with protein, in case you're protein sensitive. Get it in better condition first. Cowash, put on the deep treatment, put on a plastic cap, and apply heat all over the cap for at least 15 minutes, more if you can. Remember to make sure the deep treatment has no silicones. Good luck.