I also have migraines and headaches. Though I think a good portion of my problem is associated with structural problems in my neck. Topamax is very popular and from what I heard has a couple favourable side effects.
Magnesium and calcium should help with twitching. I belevie it is magnesium oxide to stay away from as it's not absorbed well, and you may have frequent trips to the loo.
Magnesium citrate is a better choice. I take a mag/calcium combo that help me with cramping in calf muscles at night.
Regarding headaches, aside from the Topomax, getting proper sleep and practicing relaxation should help tremendously if headaches are associated with stress and tension.
All the best