I read that the humidity in the tank should be 30-50%. On the basking side it was 21% and on the cool side 40%...is that typical for it to be lower in the basking spot? What is too low?
Yes, that is pretty normal for the humidity to be lower on the basking end, since the heat will
dry it up a little more than on the cooler end.
Those levels should be fine, no problem at all. I wouldn't want it to get too much under 20%
or so on a consistent basis because that can sometimes lead to dehydration or just a harder
time with shedding.