MyISAM table row size is bigger than the sum of all the columns size?
That's because you're using a CHAR column type; this is a fixed-width column; regardless of how much data you put in there, it'll always take up exactly that number of characters in the data store.  It is designed for columns where you'll always have exactly that number of characters, because it's more efficient in that specific case.

What you want in your case is VARCHAR; it'll make a note in the column data of how many characters you're storing, and only take up that amount of space in the data store.