Adding/Removing Breakpoints

Q1
I apologize if this is not the right area to post this but I am curious what others have done to accomplish adding/removing breakpoints.

Q2
Being familiar with Bootstrap is there a quick way to revert the max media queries to min and no max?

Here's what i was hoping to achieve, not the small breakpoint has no max:

`$viewportIncrement: 1px;

$small: 480px;
$medium: 768px;
$large: 992px;
$xlarge: 1170px;

$postSmall: $small + $viewportIncrement;
$preMedium: $medium - $viewportIncrement;
$preLarge: $large - $viewportIncrement;

/================ The following are dependencies of csswizardry grid ================/

$breakpoints: (
'medium' '(min-width: #{$medium})',
'large' '(min-width: #{$large})',
'xlarge' '(min-width: #{$xlarge})'
);
$breakpoint-has-widths: ('small', 'medium', 'large', 'xlarge');
$breakpoint-has-push: ('medium', 'large', 'xlarge');
$breakpoint-has-pull: ('medium', 'large', 'xlarge');`