It says you're using 1944x1944 resolution files in the editor window. That's not good. And by the way, it's not 2024, it's 1024x or 2048x. I also found that I do not need to export the model twice, but rather delete the first .msh file that is generated, then reload the model in the model viewer.
There's no real way of making .dds files on Mac. .dds files are DirectDraw Surface files, primarily used for DirectX, which is a Microsoft software. There are alternatives though. Personally I have a VirtualBox virtual machine of Windows 7 that I just boot up, export the files, then shut down.
You should be able to get one for free.
VirtualBox is free and you can download a Windows 7 .iso (
64-bit or
32-bit) from Microsoft's websites. You won't need to license it, I'm pretty sure.
I also have a bootcamp partition of Windows 7 for when I need that, which I can use but the VM is a lot faster if I'm working in my Mac environment.