Many of the ladies I know with thin and due hair seem to love magnesium sulfate. I heard some good things about the Beautiful Curls products for this.
As far as change in curl pattern, some people see drastic change and others don't. I suspect it has something to do with how healthy your hair is to begin with. My curl pattern didn't change much at all.
Long hair doesn't have to necessarily mean weighed down hair. Layers are a huge help do eliminating weigh down without sacrificing length. The biggest difference I saw in my curls was when I went from strictly long layers to a mix of long an short layers.

3a/f/iii
Modified CG since 11/5/11
CLEANSE: VO5 Vanilla Mint Tea Clarifying, DevaCare No-Poo, CHS Treatment Shampoo
RO: DevaCare One Condition, SS Caitlin's Conditioner, Mop Top Daily Conditioner
LI: SS Repairing Protein Treatment, CHS Silk Leave-In
STYLE: Re:Coil, Curl Keeper, Deva Ultra Defining Gel, Curls Rock Amplifier and Strong Hold Mousse, Sweet Curls Elixirs Okra Gel and Hard Hold Gel, SS Curl Enhancing Jelly and Firm Hold Gel