#3
I generally tighten up the nut and apply a drop of superglue, you can break the seal easily with a nut driver if you have to remove it later, but the nut wont back off otherwise.
Takes a Knockin' and Keeps on Rockin" DOA #08-01502
#4
you could try a drop of super glue, but just a drop so you can break it loose if you need to take it off for any reason.