*1.Generally, 小不点 is a nick name used by the older without age line, you might use them to the infants, little kids, even teenagers if you are way older them them, you use this word means you love them, you care about them, but of course you do it a right way like with a nice smile on your face.
*2. 小不点 is used to without emotional factors to describe someone is physically small, but seldom people enjoys being described in this way.