Has prity much the same sort of behaviour and growth of an Oscar so prity risky long term with most cichlids in a 75g but possible while still young to grow it on with other not too agressive guys.
Can be bred in 75g tanks but long term needs something to suit its max size of 16". http://www.cichlid-forum.com/profiles/species.php?id=9
To be honest I can not see anything wrong with your guy.
Can be. But then breeding Oscars kill of most stuff in the same tank too.
Some single Jags can be sweathearts if not mixed with stuff they can fit in thier mouths or stuff that looks like them in 6 foot+ tanks.
Agression wise they are not in the same league as some other big Central American cichlids.