My favorite pad in cold weather, and especially on snow, is to augment my regular closed-cell foam pad with a piece of Reflectix duct insulation. It's available in 24" wide rolls, and the extra can be used for a pot cozy or even its intended us as duct insulation in the home.

Nobody can predict how you'll feel in a 40F bag on a 35F night. Much will depend on your fitness, hydration, and food intake.

The hot water bottle trick in the sleeping bag is a real good one.

I've noticed there's a break-even point on wearing clothing to bed--too much will restrict your movement and actually make you colder.

Sorry for repeats, I haven't read every post.