Walbro Metering Needle
#2
I wouldn't think it matters unless there is a lot of pressure built up in the tank .in which you can install a breather valve!
#4
are you sure the tip is not silver color over the rubber tip ? I have noticed a silver coating on some needles that makes the needle appear solid. Push gently in the tip to check so as not to deform it.
#7
I noticed the silver coating starting about 10 years ago on the Walbro kits and soon after on some of the Stens kits . The coated tips always seem to work and I have noticed no stuck needles like happens on the uncoated needle tips . I think the coating is actually teflon or something similar