Don't Help The Eggs. Seriously. It can take a super super long time from "pip to zip." One of my ducks took over 48 hours. If you help them, you can kill them. They have to wait to absorb all the yolk and for the blood vessels in the membrane to dry up. They also have to gradually work around the inside before you will be able to see progress on the outside. Taking them out to check on them will do much more harm than good.
I know it's hard. I kept taking mine out the first time, despite all the advice to the contrary, and I'm pretty sure that's why they had such a hard time (one didn't make it at all and one required help after a very, very long wait). The membranes get dried out very quickly from the drop in humidity, and the temperature fluctuations don't help much either. ESPECIALLY once they've started pipping, they are very vulnerable to moisture changes and drying out.
Unless you can see the chick poking its nose out through a true hole (not just a cracked area on the shell--an actual hole) and it makes absolutely no progress and doesn't change position (but is moving, cheeping, and obviously still alive) for 24 hours or more, there is absolutely nothing you can do that won't cause harm. If it is just barely pipped, you aren't likely to be able to help it without killing it anyway.
It bears repeating (mostly because it is so hard to actually do): KEEP THE LID ON. Your babies are doing just fine. Really. It will feel like forever, but they really will make it out on their own if conditions are right. Since you've had it open already some (because of the ants and the understandable desire to check on them & help), it probably won't hurt to mist the inside of the incubator very quickly with WARM water from a spray bottle, to get the humidity way up. HOWEVER, wait to hear from chicken experts before doing this--I have ducks, and their moisture requirements are different, so it might not be a good idea for chickens. Still, there might be something you can do to undo some of the disruption they've already experienced.
Keep us updated!