Hatch Trauma -- need some feedback

So I had incubated 12 Guinea eggs. I had a still-air incubator and kept the temp up to 102. Humidity hovered around 50% according to one hygrometer, but I kept all water trays filled, so figured it was fine. On day 24 I upped the humidity by adding wet sponges. On hatch day eggs started moving and chirping and then pipping, but by morning of 27th day only 3 actually hatched. 5 more eggs pipped, and some zipped, but no further progress, and by appearances membranes started to dry around pipping site. I started running the shower (incubator was in bathroom) and upped humidity to 80%. When the movement and chirping stopped I panicked and picked off the shells off them. One was already dead and the rest was stuck to the membrane so the process of getting them out was rough and bloody. Three chicks are now ok but weak. One chick has curled in claws and limps around on them. It also has what looks to be a hernia on the underbelly. But it is in constant movement, determined to stay alive it seems. Autopsy on the remaining 4 showed 3 more fully developed embryos -- dead, and one partial. What I need to know is What went wrong? Why was the hatch so difficult and results so dissappointing? I feel that the 4 keets I helped out would have died had I not pulled them out and soaked and pulled away the stuck membrane. I had humidity soo high in the end I was worried they would drown. What went wrong? It was so traumatic, not fun at all.