I recommend reading the manual, looking at the Facebook page etc and looking at what Joe Taylor and the other developers say about using the waterfall to determine signal strength and signal quality.
Hint, waterfall signal look overpowered, wide, etc? Turn down receiver RF gain.
Not sure about the KPA1500 but I believe the limit on the KPA500 is
90C. It is normal for the fan to come on and speed up automatically at
particular temperatures. I set up some of the macro buttons in the
KPA500 utility for various fan speeds. If I run a high duty cycle
digital mode, I will kick the fan up on the highest setting before
operating. Don't think I have had it up to 75C, but it will usually run
in the 60s if making lots of back to back QSOs.