Would the males have to be separated after they hatch to keep from fighting each other and with Dad?
Well it's not like the babies hatch one day and all the baby males start fighting to the death the next day. So for a while at least all the babies could be kept together. I've never actually bred bettas myself so I couldn't tell you how long they could be kept together until aggression issues would begin.
I also have no idea about the aggressiveness of the dad towards the babies after they hatch.
Actually, I would prefer if they didn't breed.
Then don't keep males & females in the same tank.
Or if they did, would any of the other fish in my tank eat the eggs?
Again, the eggs are kept in a floating bubble nest that the male will guard to the death. So the only way any fish could eat those eggs would be if the fish is large enough and aggressive enough to kill a male betta.
--Would it be better just to place him in the 55 gallon community alone? The reason I was going to add the 2 females was to keep him occupied and to keep him from bothering my other fish. I'd rather not set up a special tank just for him, and I hate keeping him in the jar.
Bettas have very individual personalities, but in general, yes it is possible to keep bettas in community tanks without issues. I have kept both male and female bettas (never at the same time) in community tanks; most have worked out, but some haven't. Bettas are notorious for having very individual personalities--that is part of what makes them such great fish to keep. But the negative side of this is that when it comes to questions about how they get along with other species, there is simply no way of knowing until you try.
I will say that if you are going to put a betta (whether male or female) in a community tank with other fish, it is probably
more likely to work out if you add the other fish first, and only later on add the betta. Because if you add the betta first, and the betta gets used to having all 55g all to himself (or herself), then when you add other fish down the road the betta might perceive them as "intruders" into his/her territory. Whereas if you plop a betta into a tank that already has other fish, then the betta is more likely to just accept the fact that those fish are part of the "environment" and that they don't pose any sort of threat/challenge.
Also keep in mind that when it comes to male bettas & community tanks, you want to avoid any fish that are fin-nippers, as they will find the long flowing fins of the male betta too much to resist. So rather than the male bullying other fish, you can have the opposite problems--other fish harassing the betta.
What about a 10g? Just for him and his lady friends.
Absolutely not. Because if they were to breed, the betta will kill the other two females, as a 10g is too small for them to get far enough away from the bubble nest to be no longer considered a threat.
If all you have right now is the male betta, then you really have two options. You could simply keep him alone in the 10g all to himself (or with non-fish tankmates that are unlikely to draw his ire, e.g. nerite snail or two, etc.). Or else you could keep him in your community tank, and if after a couple of days in there it doesn't seem to be working out, then put him in the 10g.
If you've already bought the females as well, then I would probably suggest keeping the male in the 10g and the two females in the community tank. And then down the road if you decided you ever did want to breed them, you could move the female of your choice into the 10g tank, wait for them to breed, and then immediately move her back to the community tank.
It's also worth noting that when it comes to females, it's best to keep either only one, or else a small group of 4-5 (sometimes called a harem). The reason is that the females will fight amongst themselves (not violently like males though) in order to establish a pecking order. When there are just two females, then there is the danger that the dominant female will harass the other one too much. Whereas in a small group, the dominant female will spend a little time harassing all of the others, but her attention will be divided between all of them so that none of them is on the receiving end of it all the time.
I've read that if you place 1 male with 2 females he will divide his attention amongst them. This in turn keeps him from being aggressive towards the other fish in the tank. Is there any truth to this? 
