Sorry, I never saw your edit.
Glad you got the theme working 
There is a known bug regarding the uploading of logos in Magento 2.3. Check the end of this post (Changing logo in magento 2.3.0). It should be fixed in the next patch (2.3.1) which is due at the end of the month. But the post I’ve linked to explains how to “fix” it in the meantime.
See how you get on with that.