Hello,
Perhaps a wild idea, but since Syntorial is a video game of sorts, have you considered selling it via Steam?
The background is that while the product itself is awesome, the experience of installing and updating it is 'meh': download a ZIP archive, unpack an MSI installer, click through the dialogs, wait until it copies the files etc. - this feels very old-school. With Steam it's all much more smooth, updates just happen in the background. I get it that Valve takes a hefty fee, but it'd be also a way to attract new audiences.