It looks like you may be able to uninstall the agent from the Core by using the UninstallWinClient.exe found in the ldmain share on the core server. Just make sure to use the /NODELCBA switch per the article below - sounds like you may break some things otherwise.
As for the alert ruleset, I'm not sure if this will work or not, but it's worth a shot. From here -> Re: Blank page for Alerting - Edit an alert ruleset
Check this folder on the core: \Program Files\LANDesk\ManagementSuite\alertrulesets
There should be a bunch of XML files there.
Then from a command line, try to run
alertruleset2table.exe -v -c "c:\Program Files\LANDesk\ManagementSuite\alertrulesets"