Hey Davy,
If you don't want EasyBlog to use it's own styling and want to rely completely on the template, there is this setting which you can disable.
Settings>Layout>General>Include Theme Stylesheet on Front End
But if the template is not able to fully style the blog, then you will need to enable it back to rely on EasyBlog's styling.
Most custom css can be modified to work, so it's best we examine them case by case.
I don't want to select the font in easyblog. I want the font of the template to be used.
You may try disable the following setting. Users will not see the font option on the composer side panel.
Settings>Editor>General>Allow Changing Font Styles
There is another setting below this setting, which is
Enforce Font Style. This will set a fixed font size on the front-end, so just change the value to the one your template is using.