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.
If you change your mind down the road count me in for a purchase.