Hey,
1 - yes, it's done automatically, you can set the retired time.
2. -
http://docs.phpvms.net/development/00_how_addons_work#how_controllers_are_laid_out
Everything else is in templates in the core/templates folder, any HTML you see
3. - yes, you can, you'd have to modify the registration function, but that should be straight-forward.
4 - just have a link to it, and you'd have to manually skin your forum to look like your phpvms skin. Though, in the addon board, simpilot does have an integrated forum addon.
And I'll look into that last one, can you add a bug to the bug tracker? Thanks