Great post, Jon!
Saving Your Brain is a fantastic book by Jeff Victoroff, M.D. He reviewed 14,000 medical research studies to write that book. He's also the Chairman of the Scientific Advisory Board for Nolan Bushnell's new company, Anti-AgingGames.com.
I would add to your list above: not smoking; being within 5-10 lbs of your ideal weight; partnering with a doctor who is both proactive and focused on prevention; getting an annual checkup with tests that can spot if you have Vitamin D, E, B12, calcium, or iron deficiency; maintaining regular social contact with your friends; buying cars with a good safety rating (in one study the chance of getting Alzheimers was 4x higher in people who sustain head injuries after the age of 39; doing activities that are new and mentally engaging (helps keep the brain's plasticity). You said this but I wanted to stress that the activity should be new because that's what helps the most.