I know it's not exactly right to edit another user's page, but I was wondering, if for the sake of fixing redlinks, it was allowed? (i'll still internally cringe while doing so, it just doesn't feel right.. even if those users haven't even been active for 5-6 years)
and what about the template example pages? do I just link them to Community Central's/Wikipedia's page of the same name?
there's got to be a way to fix all of this without making someone lose their freaking mind
While I don't know about user pages, I've regularly seen admins update outdated/broken links on user talk pages, so I don't see why it should be a problem if you are the admin. Just make it a rule on the wiki to not have redlinks on user pages.
As for your second issue, that would probably be the best idea.
I'd make that top wanted page a redirect to save giving tons of users message notifications.
For most of the template talk and documentation links, I'd just remove the links. The wiki seems to have just copied a lot of WP templates, of course their documentation is giving you redlink hell. 90% of your troubles seem to come from Template:Navbox/doc.
Editing a userpage to clean up a red link, image or template is not a big deal. Just be kind and mention it in the edit summary.