Cause for Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: error
Looks like the namespace defined in your class file does not match the one you put into the resource, there's a "Form" sub-namespace missing.

Also make sure that the class is placed in the right folder.

The reason for that error is apparently that for some reason, the specified class can't be found, so apparently the router then falls back to the service. So the _ thing is just one possible reason.

Also, there are some errors in your hook_menu(), route_name is a string, access callback can be removed and you still need the first entry for now so that you have a menu link to it.