Fireworks does work in Windows 10, but FW CS6 was developed before retina-like high resolution screens became popularized.
You might be able to fix it with:
No guarantees, though. As you know, Fireworks is an abandoned piece of software since May 2013, and it is not going to receive any updates or bug fixes.
Fireworks is no longer directly sold on the website due to the newer operating systems and hardware no longer supported that well or at all in Fireworks.
In short, we are on our own :-(