No, it is not. 68.2% of the population is in the average span of 85-115 IQ. 15.9% is in the below-average span of 0-85.
Yep, 50% of them are below 100 IQ, 50% are above 100 IQ.
Official definition of IQ: measure average IQ of a population, then label the point where 50% of population is below average as 100 IQ points.
By definition, half are below the median. The normal distribution's median is equal to the mean, so half are below mean.