The Tabs List output should not be like the one your seeing now. The Tab List out of the box does not display as stacked and the bullets should be hidden. Broken Layout issues are usually caused by syntax errors in custom HTML. Using a HTML validator, I could see a lot of broken HTML like in the screenshot below.
Would you mind saving your page as a template using the Template Manager. Then, create a test page and load the template in the test page and remove all the elements except the tab. If this fixes the tab, this means that the broken HTML is somewhere in the deleted sections. If this issue persists, the broken HTML must be in the tab.
If you've found no broken HTML, the problem could be in the third-party plugins. In this case, I recommend that you copy your site in a staging server so you could test deactivating all third-party plugins and remove all the custom code you have added to your site.
If you've done the tests and the problem persists, please give us your staging site's WordPress Login URL, Username and Password.