Not too familiar with elemental damage values (whether to add both non-elemental and elemental stats together to determine the total attack or defense and whether both are used at once in attacks or only 1 is used depending on the skill type)
For the multipliers, it just shows the growth of the character. They upgrade with stars and rank promotions. Not particularly useful unless you have 2 heroes of exactly the same star and rank to have fair comparisons on who will develop more in which stat. You can look at the character to see the stat distribution in the multipliers and see which stat it specialises in (though you can just look at the numbers directly too).