On Line 175 and 176 of main.js:
$('td:nth-child(' + show + '),th:nth-child(' + show + ')').show();
$('td:nth-child(' + hide + '),th:nth-child(' + hide + ')').hide();
It looks like you are trying to swap out a column here, but your selectors aren't quite right. In particular, it looks like when you se the nth-child value to "2", you end up selecting another, larger td element. Which is why, after you call hide(), your layout breaks.
Try changing your selector to better specify what you want to show or hide. For example:
$('#advantage-calculator td:nth-child(' + show + ')').show();
$('#advantage-calculator td:nth-child(' + hide + ')').hide();
(I'm not sure why you were selecting th
's in the first place so I took those out)