When I fire him, can he swithch back and charge me hourly for his work performed?
NO, BUT HE HAS A LIEN FOR THE REASONABLE VALUE OF HIS SERVICES.
Can I get my complete file from him upon firing him or only after I pay him?
YES, STATE BAR RULES REQUIRES THE LAWYER TO RETURN YOUR FILE PROMPTLY ON TERMINATION AND REQUEST, WHETHER YOU OWE HIM MONEY OR NOT.
Can I wait and pay him when the case settles?
HE'LL HAVE A LIEN ON THE CASE FOR THE VALUE OF THE WORK HE DID.
What all can he charge me for and do you have any general idea of what I may owe?
CHECK YOUR WRITTEN FEE AGREEMENT, IT SAYS WHAT FEES AND COSTS YOU'RE LIABLE FOR. WITHOUT REVIEWING YOUR FILE TO SEE WHAT STAGE THE CASE IS IN AND WHAT YOUR LAWYER HAS DONE, NO ONE CAN GUESS WHAT COSTS YOU OWE AND WHAT LIEN YOUR LAWYER MAY HAVE.
You may have a hard time finding a new lawyer, depending the various factors, one of them being the fact that this lawyer will have a lien on the recovery and you can only be charged so much in total fees, so there's not as much for any successor lawyer.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.