Can you post another photo ---- have difficulty seeing it clearly. But from what I am seeing, the private part is not rounded. Likewise. It has more of a triangular shape and kinda small. Based on this, your Frontosa is a male.
Pointed dorsal fin and length are not accurate way of sexing them. I have 2 colonies of adult males, I can't distinguish females from the beta male based in length of fins. All of the Frontosas have pointed dorsal fins.
The he alpha male has really long trailers, but not true with the beta male.