RoaringApps lets people know with which versions of OS X/macOS their apps (that have been reported on) are compatible, but I thought they'd get feedback from more than just a handful of users.
No, DW CS3 is NOT working OK in High Sierra, possibly because of the problem you've run into.
I can't answer your last question without your telling me when DW CS3 was released.
More: You also need to check the Parallels documentation to see with which OS versions it's compatible.
Last edited by artie505; 05/08/19 05:25 PM. Reason: More