PE exam passing rates are fairly consistent. The passing rates vary substantially from discipline to discipline, and from administration to administration. See this table of passing rates. Neither is true. There is no discernible pattern to the subjects or difficulty level of the exams.
States are free to set their own passing scores.
Most states don't have the expertise to set passing scores. The PE exam is graded on a curve. No, not true. No, not true. The number of people passing is not a factor in setting cut scores.