I usually aim for 70-75% because I am fairly hands on so if I do feel I need to assist it doesn't usually go below 60-65% when I quickly open the lid. Higher than 75 makes me nervous but I've heard of a lot of people having the humidity shoot up really high when the chicks start hatching so hopefully it's ok.
Those look like they are shipped eggs right? They can be tricky to hatch sometimes, I've had quite a few babies from shipped eggs that needed assistance unlike the local eggs I've hatched which usually do a really good job of hatching on their own unless the eggs were old when set. I have an incubator where I can position the eggs so I can candle through the incubator window to check for progress. I always note when they internally pip and base if I should help or not on that. In your position since you have no eggs that have externally pipped and you don't know if/when the remaining eggs internally pipped I'd candle the remaining eggs and if you have one with an internal pip I'd add a very small safety hole at the very top of the blunt end of the egg where the air cell is, that way if the chick is malpositioned in there it will at least not suffocate. Doing so may increase your likelihood of having to do a full assist later though so you'll have to decide for yourself if the benefits outweigh the risks.
Here's a great article on assisted hatching if you decide to go that route. I've personally had a lot more successes than failures in my assisted hatches.
https://www.backyardchickens.com/articles/guide-to-assisted-hatching-for-all-poultry.72886/