Your questions are difficult to answer, as there are no national standards for polygraph operators, nor are there national standards for post-conviction polygraph "testing." If your state requires polygraph operators to be licensed, then you could check what rules may be applicable. Such information is often available on-line. But it would probably be best to consult with a lawyer regarding your husband's rights where the polygraph is concerned.

That said, it is not unusual for a polygraph to have three relevant and three "control" questions. Typically, a few irrelevant questions, and perhaps an unscored "sacrifice relevant" and/or "symptomatic question" will also be included, for a total of  10-12 questions.

my husband was asked post sentencing to take a lie detector test.  the examiner only asked 6 questions, 3 control and 3 in regards to the crime.  because of one question which they had discussed prior to the test and to which my husband stated he was not sure, his test was considered inconclusive.
is there a set amount of questions an examiner needs to ask?
if asked for a retest can the examiner refuse?  which by the way he did.
can an examiner ask how to word questions so that the examinee will pass?