If I have not sent you the article from PP mag, on hatching, pm me your e-mail address and I'll send it to you.
As for the 109. I think rarely are the temps exact in these things. Though I've only used a 1602N twice and neither time things went well. But that was before I read this article and realized some of the mistakes I was making.
If you are early in the hatch, then candle and see what's going on. If you are past day 15 or so , you might as well see things through to the end.
You don't say whether your using a digital or not. These are better IMO.
Temps of 100.0* - 101.5* should not be a worry. In fact IMO are best. 99.5* seems to me to just be a guideline as are the degrees of humidity. Even a hen can't hold her temp. even through to the end. She gets off once a day and surely that doesn't hurt.
IMO it's the health of the eggs, that is the reason for some losses.
Take care and keep us posted,
Rancher