Hello mikemarco,
Thank you so much for using our theme AcmeBlog.
1. The recommended size for logo is 290*70, so please make the logo with this size and add it.
2. You can change he logo size from acmetheme/core.php file, you will find the code for custom-log, you can change the height and width there.
3. Please try the one method and if not worked, try once by making the width of logo to 100%. Have a look here for details.
Let us know, if you faced any problem again. We are here to help you in every situations.
Warm Regards,
Acme Supports