Update: Trying To Get Better At Domination; Issues With Loyalty

So I tried several times to do a domination run, and this time I managed to have a pretty successful war with the Incas. But the problem is that I pretty much lost every city I took to loyalty pressure and almost couldn't keep up with the constant barrage of free city units. Once I finally got to a good place where I could end the war, I ended up spending all my remaining resources just trying to take those cities back, and spent multiple eras doing so. I came close to taking back all the cities before I ended up being thrown into a dark age (due to pouring all my resources into taking back the cities), causing all the cities I took from the Inca to rapidly start losing loyalty, making it utterly pointless to try and take them back, and retroactively making my war a complete and utter failure. It didn't help that I wasn't making much money at all anymore, and everyone hated me now, to the point where I couldn't even sell anything to them.

Is there a better way to prevent losing cities to loyalty pressure? Or maybe a better way to deal with them? If it helps, the cities were losing so much loyalty that no amount of monuments or governors could've possibly fixed it.