What have you customised so far to get the display you have currently and how does this not meet your requirements?
It looks like you have added css rules to modify the output of the plugin, but have not followed the recommended method outlined in the documentation. If you are using custom rules to modify the output of tabby responsive tabs, you should follow the instruction to remove the default tabby stylesheet and add the css rules to a child theme stylesheet and then make changes to those rules.
This recommendation is to ensure that additional rules to modify the plugin's default do not cause display issues if the default styles change in a later version.
I may be able to make some suggestions to achieve the display you require if you can provide some more information and ensure that any modifications are made by the recommended method, however setting the width of the tabs was not a consideration when the plugin was created so this support for css customisation is probably beyond the scope of the free support I can provide for this plugin.