You are at a difficult stage and I agree with everyone else here that those swings are not helping at all. Consider them the enemy.
I'm a stay at home dad of 21 month old triplets and I got them to sleep through the night by 4 months. Some of it was luck in having good babies, but the rest was because my wife and I really pushed for them to be independent.
Nap times were all me and I always preferred the kids to sleep around 3 hours in the middle of the day. With all three of them in the same room, I couldn't guarantee they'd sleep that long, but I knew how long I would leave them in there. If they chose to play/cry/babble for an hour or two, that was fine with me. I knew that eventually they would fall asleep, and they did. After about 2 weeks of doing this, they started to fall asleep quickly and get almost 3 hours of sleep during the day.
Bedtime was very similar. We had a bed time for them of 8:00PM and we put them all down together. Initially there was a lot of crying, sometimes for two hours or more, but that two got to be less and less and then eventually they would fall asleep within 15 minutes or so.
To help them make it through the night, I fed them a full meal AND gave them between 8 & 10 oz of formula so that they had full bellies when they went down and were less likely to wake up hungry. To be sure they did start waking up every couple of hours, but unless it was a serious cry (all parents know that one) we left them be for the most part.
Occasionally my wife or I would go in and pick up the crying baby and hold him/her for about 10 minutes and get it calm and put the baby back in its crib. We wouldn't leave though, we would stand above them and lay our hand on them with the slightest amount of pressure to help comfort them. My one son loved it, the other son didn't care, and my daughter absolutely HATED that, and it didn't them long to let us know this.
Now, it wasn't always perfect, and there would occasionally be an odd baby that would wake up, but we would just let them cry and go back to sleep. Once they're sleeping consistently through the night, that will hardly happen and when it does it won't last more than 10 minutes or so (unless there is a serious problem like being sick, scared, or having a bowel movement that hurts).
Now at 21 months they still share a room and they NEVER seem to fall immediately asleep. They play with each other, sing, babble, and cry. My one son in particular must think he's giving a concert sometimes and is often up for over two hours playing and yammering away. That's his choice because he's not getting back up (which he knows) and he will not get up in the morning until it's time for all three to get up and if he hasn't had enough sleep, so be it (that's a whole other game right there!!)
My basic tenet about them sleeping, whether for a nap or the night is this;
I don't know how long you'll sleep, but I do know how long you'll be in bed!
It might sound a bit harsh, but it's effective, it's consistent, and they are getting the right amount of sleep each day.
If you need any other advice or just some support, feel free to give me a shout.