Sprocket size and chain forces

Hi, I'm having a little trouble wrapping my minds eye around the forces in a chain and hoping someone can verify that I'm on the right track.

I have two sprockets, each with diameters about 3 inches (radius of 1/8th of a foot). If I am transmitting 100 lb-ft of torque then the tension in the chain would be 100/(1/8) = 800 pounds. Correct?

Second, If I double the diameter of both sprockets to 6 inches, then I halve the force in the chain and could use a chain with half the strength, correct?

Presumably the larger sprockets would cause the chain to be running at a lower temperature as well?

Okay, now what happens when I'm transmitting 100 lb-ft but it is running at 6000 RPM. Would I still see half the force in the chain using the larger sprockets?