There are many conflicting opinions about whether structured data directly helps in a FAQ page's SERP ranking. However, there seems to be consensus that rich results produced, in-part, by structured data can help with click-through-rates which then indirectly boosts SERP ranking.
According to Moz , "Whether structured data affects rankings has been the subject of much discussion and many experiments. As of yet, there is no conclusive evidence that this markup improves rankings. But there are some indications that search results with more extensive rich snippets (like those created using Schema) will have a better click-through rate ."