Mine usually hatch 11-12 days after being laid, and mine are in plain sight, so I don't miss the spawn day. My tank runs about 77 degrees, but I am slowly raising it up to accomodate the spawners.
Mike, I'm hoping the temp in your larvae tank doesn't swing by 3 degrees a day too. I have one of those cheap Coralife digital thermometers ($5.99) on my larvae tank and it swings maybe .5 degrees (.2 degrees either way from normal, which is 79.0 degrees). These aren't the most accurate therms out there, but they will tell you how consistant you are. I use a cheapo 50W heater right above the airstone.
The rotifers really are the key Mike, I don't really think you have any other problems outside of nutrition. I bet if you had a bunch of rotifers in the tank the morning of day one, you'd see a vast improvement in survival rates.
Do you have any green water, Instant Algae, or anything to feed Rotifers? If you can keep them fed, I'd send you enough to start a co-culture in your rearing tank. As long as you CONSTANTLY kept the water cloudy with Instant Algae, DT's, or some other form of microalgae or rotifer food, they would probably reproduce faster than the fry can eat them.
I usually get my density up early, then add fresh grown nanno chloropsis about 3-4 times a day, the fry get fat, and the rotifer population sustains itself (I'm not talking 200 fry here, between 15 and 50). Then 8 or 9 days later, I switch them to newly hatched brine shrimp (easy and cheap) and I have 11 of them through metamorphasis (out of 50) and another 16 getting ready to start.
You could also start a Rotifer culture with some of them in another tank / bucket/ anything that holds water.
Jason