All our trucks have multiple EGT's. There is one that is post turbo which is what most people read (think it's Bank 1, Sensor 1). You can read this with an OBDII scanner. Many here buy a cheap bluetooth from Amazon that you just plug in, then download your choice of app to your phone. I use OBDFusion on my iPhone, think the app is $5-$10.
As for temps, it depends wildly on many factors and what you are doing. I think generally most agree to keep the EGT temps below 1100 sustained. You'll peak higher but should cool down. When I tow my 24' enclosed race trailer I'l occasionally see peaks of 1100 degrees but generally while towing on the highway's I average in the high 800's, low 900's. There are a ton of safeguards in place on our trucks and it'll start to defuel when a sensor hits the danger zone, EGT is one of them. I don' know at what temp or time frame the truck will start defueling based on EGT.