If we are talking severe damage then a "deep trim" as nurse called it
might be your best solution. However,
judging from your signature picture your hair doesn't look damaged to me by any means.
Other options--a deeply moisturizing conditioner could really help. I don't know if you're familiar with the Aubrey Organics line, but I cannot beat their Honeysuckle Rose or Jojoba & Aloe Conditioners as far as moisture is concerned. You mentioned the Damage Remedy line from Aveda. It is great and I AM a fan, but it is not as moisturizing as the Aubrey conditioners I just mentioned.
Then when you do flat iron, is your hair length even? I think most naturals don't have even hair when it's straight. That could be bothering you regarding the appearance of your straight hair. I'm sure you use something on your hair to flat iron. (I'm assuming you flat iron and don't press--if you're pressing, CHUNK the pressing comb outside somewhere NOW!) Anyway, jojoba is great when flat ironing. So is Dudley Cream Press. The jojoba is light. The Cream Press is heavier, but oh it is just wonderful. It makes the hair so smooth and soft and luscious.
I bet it would be great on heavy, thick hair like yours.
Please let us know how things progress.