What options do I have with this only witness ?

It's really difficult to tell without some additional information. Is this a criminal matter? Civil? What is the subject of the testimony? A witness might have a weakness or may have said the wrong thing but it may not impact the weight of their testimony - it depends heavily on the circumstances of the case and what you are trying to prove. Not sure what type of case this is, but speaking to a lawyer can help sort out how this could impact a case.

If this is a criminal matter you should be addressing this question to your attorney. If you don’t have an attorney, that should be your first priority, even before dealing with the witness.

Your question is ambiguous. If your attorney was doing the deposition, you should ask him.

Options with this witness? The only option I can think of is that the witness can be cross examined or not.

You don't have any options with this witness other than to let your attorney cross examine him on the witness stand.