Mega Menu - sub-menu styling issues

I’m trying to create a Mega Menu for my site and am running into some problems with the dropdown and submenus. For one, the dropdown box is huge when I only have 3 columns/submenus in the dropdown and I would like to shrink that to fit more. How would I do this and, additionally center the drop down so it’s not so heavily formatted on the leftside of the page?

My menu is setup in this form:

And the main issue I’m having is how it’s positioned to the left, can anyone help