How can I stop my toes from going numb on long rides?
There is probably a combination of things that can help.  Periodically getting your weight off can help as can making sure your pedaling stroke includes ankle flexion.  In my experience, that helps a lot with circulation in my feet.  Obviously, you'll want to make sure your shoes are not laced or velcro-ed too tight.  I will often stand in the pedals and do calf stretches by flexing my ankles up and down (still clipped in) to help with foot circulation.