Is that admin the server owner, then (Maxite, apparently)? To fix the 'at the expense of driving off real users (by way of flooding the Recent Changes list with endless deletions and blockings)', just do all the blocks and deletions using a bot account, then they won't show up in RC by default.
Until you have server access, I don't think there's much you can do. Perhaps putting together a bot to fight it off automatically would make things easier, though it's a little ambitious...
While I was poking around, I made an account and noticed a couple of things:
- The link to the captcha help page from the create account page doesn't work.
- When you're logged in, the logo is over your user page link, so you can't click it (easiest way is to click on talk, drag off and release to avoid following it, then shift-tab, enter). This happens for a browser width around 1250px and below for me.