do the police have to get a specific warrant to force ably open a locked safe
You always start by looking at the warrant itself. Does the warrant authorize searching locked containers? Search and seizure questions are something that you will definitely need professional help with. Contact a criminal defense attorney and go over the facts of what happened. That way they can give you an answer tailored to your specific case.
That depends on what they are looking for, what information was given to the Judge that issued the warrant and what the warrants wording says. It is very possible that the warrant didn't include the locked safe but with the limited amount of info here no way to tell. Get an attorney and make the argument for sure.
As my colleagues have mentioned, it depends on the specifics of the warrant. If the police exceeded the scope of the warrant, it could lead to suppression of some evidence discovered. An attorney will know how to research this issue in full and submit a suppression motion if appropriate. If you don't have one already, I would recommend consulting with and retaining an experienced trial attorney.