1) i would say no to even a single dovii.
2) yes Jags will most definitely recognize their owners. they're really really smart, even for cichlids. they can recgonize people from around 7ft away. I've even heard stories on MFK about a jag that would go ballistic if somebody in "their room" was wearing a hat and would go crazy until they took it off. (so they definitely have individual personalities too)
3. If you wanna breed jags just a warning, they might claim the whole 180 as their territory. If i wanted a pair I'd go pick up 6 or more young ones and wait for a pair to form as they mature. (don't worry, young jags are usually really inexpensive, around $3) Then rehome the other jags once i haved picked my pair. If instead you'd prefer to not wait to grow them yourself it might be a little harder to get a pair, but is still definitely doable.
4) if you do decide to go with buying adults, and adding them to your already established cichlid territories, there are some things that you can do to help them from being picked on. First i would feed all of the potentially aggressive fish that already have established themselves in the tank. Second i would move the tank decor around so that their are no territories anymore. Yes i would definitely introduce the smaller jag (which will probably be the female, but get them as closely sized as possible). Let her get comfortable for a few weeks, and then do the same procedure when you introduce the male.
5) when breeding any parachromis, always have a divider ready just in case