Looks like you've gotten some good advice here. The method you are using for assisting is one I have had to implement quite a few times and I find it to be fairly safe and effective if done correctly (I've really upped my hatch rates with shipped eggs that make it to lockdown by using this assisting method). The most important thing is to not get them out of those eggs too soon and know the signs for when they are truly ready to come out. Hopefully they will be able to pop right out on their own when they are ready but I've had plenty that need help with getting out as well. It could be awhile before those little ones are ready, I'm seeing some fairly large blood vessels on some of those membranes. Once the blood vessels have mostly gone (they'll have dried and shrunk considerably) the chick may still need more time to finish absorbing its yolk and the rest of the blood vessels further down in the egg. All the chicks I've assisted chew/yawn fairly frequently while still absorbing the yolk. When my babies are ready to come out they often start peeping more frequently and more loudly and they will start thrusting upwards/outwards with their beak (they are trying to break the shell like they would in a regular zip at this point). Make sure they are consistently doing this and that they are not yawning/chewing anymore. I've had babies that start making a fuss and try to break the shell with their beaks that were still occasionally yawning/chewing that weren't ready quite yet (usually within a couple hours of being ready though).