Hi there,
First of all, please kindly make a backup of your website and update the theme to version 2.0.4.
After that, please go to Pro > Headers and choose the header in question. You used an Image element. Please select that element to see the options. there you will see a checkbox which will enable a link to that image element:
Upon selecting that checkbox a whole new section will be available which you can use to add a link to your homepage:
Regarding the inability to add CSS, It must be something related to a 3rd party plugin. For example, we have reports that if you use the Yoast plugin this problem happens. We will fix the Yoast problem in the upcoming release. If you have another problem we strongly suggest that you open up a separate thread and follow up the case with us to fix the issue.
Thank you.