Under normal use you will not need to clean the valve on the bottom of the cartridge. If a component contains drier and has not been used in several weeks, you may need to clean off a small drop at the valve opening.
Yes, provided the formula is saved using a name that is distinct from the standard color. For example, you can modify the standard 228 formula to accommodate a special stock by making the change and naming it something other than 228 (i.e. name the new formula 228.2).