We use fluid film for lube up here, things tend to get rusty
But I also use Wurth S2000 or transmission oil
Usually depends on the current condition of the chains and environment
I usually always keep the secondary's adjusted to where all channels are even at the top and the primary's just touching the ground when the mast is even and lowered all the way
I don't really use a chain gauge that often as it's easy to tell if a chain is worn by looking at the part of the chain that doesn't roll over the chain roller and comparing it to the part that does...
And yes I use the fork gauge