Let me try to answer some of your questions.
Firstly, NovaMind for Mac
does have the PowerPoint export feature (in Pro & Platinum edition) just the same way as NovaMind for Windows. The PowerPoint export creates a PowerPoint presentation based on the textual content of the Mind Map. It does
not export images of your Mind Map.
What the Mac version currently doesn't have is the features of the
Presenter. The presenter also includes the ability to export selective elements from your Mind Map to images which you can then manually import into PowerPoint. See
this blog post and
this one for an overview.
It is perfectly fine to create a Mind Map using the Mac version, then opening it with the Windows version, define the slides you want to export and use the image export feature of the presenter to create the images.
It is
correct that your license is cross platform so if you have Windows available you can use NovaMind for Windows too.
In the Mac version you cannot do this since the Presenter isn't available yet. We have said a number of times before that we cannot give an ETA on the presenter. The Mac team is working hard on this. Just this week they have made some important progress by
releasing a beta version of NovaMind for Mac with a completely reworked drawing system. These are fundamental changes to make the Presenter feature possible. Again, I (nor anyone else) cannot give you an ETA when the actual Presenter will be available.
Hope this helps.