I know the terror of trying to help chicks out of their eggs. I had to assist silkie chickens and button quails hatch and the quail eggs, being so small, are even scarier to assist. Doesn't help that my hands shake like a jackhammer when nervous!
Luckily I have also had a good assist ratio despite this.
From what I see, you have had very good luck in the assists and are doing very well, I also have had humidity drops in my incubator at times when eggs are hatching and pipped and am always like "Whyyy! You are meant to be at 70%, not 40%!"
Even the hen isn't guaranteed to keep the humidity up as she left her nest for a poop break right as her eggs were hatching! Twice! I had to assist the ones that had already pipped, one who looked like she wouldn't make it and looked pretty much dead for about an hour before eventually perking up, but is now a strong healthy hen. I plopped the rest in the incubator to hatch where they were more stable and later returned them to their mum when they were all fluffed up.
She didn't accept back her first batch and so I raised them, but on her second batch, she rolled the offered chick under her as if it was an egg!

From what I see, you have had very good luck in the assists and are doing very well, I also have had humidity drops in my incubator at times when eggs are hatching and pipped and am always like "Whyyy! You are meant to be at 70%, not 40%!"
Even the hen isn't guaranteed to keep the humidity up as she left her nest for a poop break right as her eggs were hatching! Twice! I had to assist the ones that had already pipped, one who looked like she wouldn't make it and looked pretty much dead for about an hour before eventually perking up, but is now a strong healthy hen. I plopped the rest in the incubator to hatch where they were more stable and later returned them to their mum when they were all fluffed up.
She didn't accept back her first batch and so I raised them, but on her second batch, she rolled the offered chick under her as if it was an egg!