Yes it could kill him, but to be honest, it sounds like he is weakening. Bantams usually start to hatch out day 18-20 in my experience. I just hatched out bantam Orpingtons, and I had one just like this situation. I went to the kitchen and got some warm water going in the sink, not a powerful stream, just enough so if I cupped my hands it would slowly fill up. The water was real warm, but not so warm that it burned my hands. Next I "pipped" a ring of shell around his head with a toothpick, carefully, and slowly. I sat him back in the incubator to check that by water temperature was stable. Then I came back, picked him up and was VERY careful not to drown him in the water. I kept his head up and was able to peel the rest of the shell off. It bled a little, but not terrible. The whole time I kept my hands cupped so that the warm water surrounded him the best I could. As soon as I got him all the way out, I rushed back and put him in the incubator. He was really weak, and I was afraid he wouldn't make it. 24 hours later he was up and walking around. He was splayed legged because I help him, but I shackled him with zip ties and by the third day out of the incubator I was able to cut off the shackles and he walked fine. It was touch and go, and I was a nervous wreck, but he is now 3 weeks old, a bit smaller than the others, but healthy and running around.