The first thing you need to do is accept that you will always have some damage because of the way you want your hair to look--and that's OK. If you want your hair straight, there's nothing wrong with that, as long as you know you're not going to have virgin-level hair along with it.
Butters and oils don't moisturize. They can improve the feel and softness, so can be helpful in that regard. Coconut oil will penetrate the hair shaft, so for your hair would be more beneficial. You can get it just about anywhere--Trader Joe's has it, Walmart, most grocery stores, etc. I would do a heavy coconut oiling the night before a shampoo, and you can also use coconut oil to help mitigate the damage from bleaching (google for more information; there's lots out there).
Your hair is probably also high porosity due to bleaching and damage, so will lose moisture quickly and needs lot of protein. The repair treatments are good; there's a homemade alternative made with gelatin that would probably be cheaper and just as effective: Pedaheh's Hair Blog: Gelatin Protein Treatment
. It should be followed by a moisturizing treatment (deep conditioning), which can be as simple as mixing regular conditioner with oils, honey, aloe vera, etc. depending on what your hair likes. This thread might help: The much-recommended SMT (Snowymoon's Moisture Treatment)
. Are you sure you actually have a scalp issue, or is it just dryness caused by your routine? Conventional dandruff shampoos can be pretty harsh, so switching to something gentler if you can would be a good idea, or even conditioner washing.
And finally, see if you can turn the heat down a bit. It will make a difference in the level of damage if you can get it down to 350 degrees rather than 400. Use heat protectant, too, of course!
Former longhair, now CG, living in N. California where the fog meets the wind
3a/b, fine, normal porosity/elasticity, high density
Conditioner wash and style, sometimes with a dab of BRHG.