If you can post some pics it would help. I haven't incubated any twins yet, as the odds of actually getting a live chick out of there are very slim. But have a look through this thread. There may be something that will help...
The air cells look good. They should always be at the fat end of the egg. When the chick gets into position for hatch, it will position itself so it can pip through the inner membrane into the air cell, where it will start breathing. It will position itself to pip into the fat end of the egg...
I'm so sorry to hear about your loss! And for that I really hope this hatch goes well for you. Have you measured the temperature and humidity around the eggs? It sounds like it's going well so far, but the final days and hatching may get interesting. The chicks will need a fairly humid...