'Add to Cart' button is squished. Didn't make any changes to the script.

Try this in your custom css:

.summary p {line-height: 40px;}

Check that you are using the latest version of your style and the genesis framework.

Thank you but where in my custom css do I place the code? In the theme’s stylesheet? At the bottom of the page?

Some themes allow the editor to enter custom css. It may be under Appearance / Customize. If not, you can use a plugin like this one though there are several other plugins that can do the job.