Birchwood Casey Barricade (formerely known as Sheath) is a great protectant
I have had pretty good luck with "Sheath" also, still have a couple of cans of the old stuff.
As for my gauges, Dillon and Wilson. I have tried to make a habit of bringing my dies, tooling and gauges inside to a controlled environment in the house. I have an old tackle box I use for a lot of my tooling. Die boxes I put in an old milk crate.
Summer and humidity is hell.
Just my regular workshop takes a beating, lathes and drill presses don't like humidity either.