do you have plans to port the game to macOS/Linux?
No, but you can use a wrapper program to play it on mac.
I would love to try, but Wine is a wilful beast...can I get a refund in case it won't work? In turn, I promise to provide wrapper (if it's gonna work), so other users would have easier time running it on Mac :)
Also, what minimum DirectX version required for the game?
I think DirectX 10, I think you have to go through Itch.io's sytem to refund the game I'm not sure how to do it on a personal basis.
It's not possible to run the game using wrapper on macOS then :( The latest DirectX version supported is 9.0c due to Apple not updating macOS OpenGL drivers in favour of proprietary Metal API...
Should be possible on Linux though.