Yes, the females can all live together (and should, they're very social animals). You can't just throw them together, though, they need to be introduced slowly. I usually start by putting the cages right next to each other. I mix bedding between the cages and give them the same dust bath to use. You should do that for a week or two to get them used to each others scents. Then you can start doing short intro meetings in neutral territory (the bath tub works great for that). The meetings should be kept very, very short at first (like a minute) as you want to prevent a fight. Once they've fought, it'll be harder to introduce them. If the meetings are going well, you can extend the time they spend together. Putting a dust bath in the tub with them is useful since degu social groups in the wild share a dust bath.
Once you're confident that they're getting along, place them all into a freshly cleaned cage with the shared dust bath. Make sure the cage is large enough for all of them (degus need a ton of space) and have one food dish per degu.
It sounds complicated but females are usually easy to introduce, you just want to go slow just in case
I would consider getting the male a buddy (a baby would be the easiest to introduce), male degus are just as social as females. I would also not recommend breeding your degus. Since they're rescues, you don't know their genetic backgrounds.