Thanks for your feedback.
I removed the grill today and doublechecked all visible screws and retightened them all a bit. Then I also removed the tweeter, checked the connection and all and put it back to the cab. So from what I can see all is well installed and looks good.
Which screws do you mean exactly? The screws for fixing the horn to the wooden cab face or the screws for fixing the plastic part to the actual tweeter (the metal part, where the cables are connected to)?
The tolex issue is a bit annoying and disappointing but can easily be fixed with some glue and a black felt pen.
Oh, I have no plans to return the cab in order to get something different. I like the sound!