I believe this specimen is male but could be wrong. Not looking to breed, just generally curious. Thanks!
The males get more blue dots while the females tend to have richer yellows and reds and the signature dark blotch on the dorsal fin 
I noticed the firemouth is it possible to keep salvini convict and acara together with swordtail dithers in a 75 if all started small?
IMO-yes its possible. Just depends how aggressive the salvini and convict are. I had a salvini, convict, firemouth and swordtails in a 55g for a long time.
Watch out for the convict. They are super aggressive, not as much as say a dovii but certainly a mean fish