I need help to find the best way to remove the old ceramic tile and thinset. There is already backer board down. Can anyone help?

You will most certainly be putting new backer board in... if the old tile was properly set, its going to rip the hell out of the old backer board when you bust it all out... and you must have a smooth surface anyway to get good results.

Its easier to rip it all out, backer board and all. And put in new backer board. Its not that expensive and its going to be easier.