Keyhole cichlid/convict cichlid/Angelfish/Discus. You can't really do any of the 'larger' S.A's, and some will rip up plants, these are what I suggest. It's a hit and miss with sevs, some munch plants like no tomorrow and others ignore them.
1000 - 1200L min for any aro IMO; kept silvers and Jardini and neither are suitable inhabitants for a 6x2x2 (which I have), In henwards 1200L the aro can move properly and looks proportionally good with the tank.
Depends on the temperament of the fish. Some ornates I found were much more aggressive than others, and they are more aggressive than the other species. Can only give it a go to find out, I think it would end up being fine.