A variance of 93° to 101° on your thermometers certainly suggest they are far from calibrated or that you have some real hot/cold spots in your incubator...
Hot temps are far more lethal then slightly cooler temps, but also it's not the air temp that is important, it's the internal egg temperature and the best way to measure that is to simulate an egg and measure it's internal temp... Many incubators will fluctuate between say about 97° and 102° as the heating elements cycle on off, and this is perfectly fine in most cases as the average temp would be about 99.5°...
Take a small ziplock bag, put 2-3 oz of water in it, remove the air, zip it shut and then fold/roll it into something similar to the size/shape of an egg with a known good thermometer in the middle of the folds/rolls... This will give you a very good approximation of the internal egg temperature... Another option and the one I use is a 2oz 'preemie' baby bottle filled with water and the thermometer inside that... There are also other DIY ideas as well as commercial egg simulators...