Damaged hair is porous hair. Some people (like me) have hair that is naturally porous, easily susceptible to damage. I also do things, like dye it , that cause damage.
Here is a link on porosity.
I agree, protein is trial and error. If you do a PT either do a DT or use a moisturizing conditioner afterward. If you get a PT that is too strong, your hair will feel strawlike. If this happens, the cure is moisture. Do deep treatments and use moisturizing conditioners.
You will just have to choose which way you want to go.
AO GBP is not strong (I believe) and has the conditioning part built right in.
Nexxus is stronger then ION (I believe) and not as strong as aphogee.
moisture vs. protein article
http://pedaheh.blogspot.com/ (a blog to help new wavies, go to the how do I get started page)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers