For Windows there is Basilisk II Build 142, which does read Mac HFS HD floppies fine.
(Ctrl-Shift-F11 is used to mount a Mac floppy in Basilisk II B142)
For DOS there is Fusion PC 3.0 running is DOS mode up to Windows ME.
OSX still has read ability for HFS floppies too, given you add a USB floppy drive.
Write ability was dropped for userland with OSX 10.6 sadly.
All three solutions do have in common, that they only can hadle 1.4MB floppies.
The old Sony drives in Macs used variable rotation speeds to squeeze 800k onto a 2DD disk.
PC floppy drives can not vary their rotation speed, 800k is a no go therefore.
For your files, SIT is a compressed one which needs to be inflated with Stuffit Expander 5.5.
DSK may be mountable via the Basilisk II volumes listing. If not, DSK can be mounted by Disk Copy.
Start Disk Copy e.g. in MacOS 7.5 and drag the DSK onto the Disk copy window on your desktop.
Boot disk: http://macintoshgarden.org/apps/macos-753-emulators
Disk Copy: http://macintoshgarden.org/apps/disk-copy
Hope this was not TLTR, good luck! Its not that hard as it may look at first glance.