Hi there! First I would like to say welcome! Now on to the matter at hand...if your hair is severely heat damaged, the only way to get your curl back is to cut off the damage and then start from there. I don't have much information to share with respect to protein treatments as my hair does not respond well to them, but you should give it a try. You will have to experiment to see what works and what does not work for your hair. If you do it and it doesn't work...don't worry. Try something else. At least you will know what doesn't work for you
. YouTube is a great place to start to get advice on tips and techniques. Again..everything may not work but you will have to try different things to find out what works for YOUR hair.
As far as products, that contain sulfates...I use them. There is nothing that says being natural means that you can't use shampoos with sulfates lol. You can dilute them if you are really worried, but I wouldn't stress about that. As long as they are moisturizing, I think you can do well. And you can always balance out your use of these products with natural products such as olive oil, jojoba oil and coconut oil.
As far as styling, I wear twist outs and braid outs ALL the time. You can do them wet or dry. I blow dry my hair beforehand, but when my hair was shorter, I would do them on wet hair. I hope this helps a little. Good luck!