Err... BB, GL came up with that only two thing long before the EU did. And he did not steal the double bladed sabre! Any more than he stole force push from Jedi Knight- they are simply obvious ideas! And, as you say, Coruscant was his idea first.
The point remains that EU is non-canon and it is only canonical stuff you can consider when talking about the films.
Itnif, stop bashing EU! GL has done some EU things in his movies.Bespin Barf, Zahn was allowed by Lucas to use Coruscant in his trilogy, and read Ush reply as well for the other things you listed.
Okay, but are you happy to say that it is canon that there are only 2 Sith and both are Lords then - the stuff from TPM?. Well the only two part came from a film and that they both are Lords, well at least the 4 siths we have encountered have been titled Lords. So since that is from the films it is cannon.