There are some graphics settings in preferences that might help. I don't think it defaults to "Fast".
I'm not sure if Robocode is equipped to run from an installed location like that. It seems entirely possible to me the package is just broken. (Note it's not necessarily the author, who'd probably know how to do it right, that packaged it.)
Keep up the good work vs Dookious. :-) He's still a pretty tough cookie.