[Mart]

I'll have a stab.

1, Dunno but it sounds like a new bush would be a good idea.
2, The plugs are domed. You put them in place and tap them (sort of) flat which expands the diameter. Don't know if sealant should be used.
3, I took lots off the valves on the crusty Flatty. The material is tough all the way through, not case hardened.