Hi, that price point will only leave out the DDJ-SZ, but that, imho, is a slightly overpriced unit with too little going for it to be of much interest to most DJs. Just me, of course.
It will also put into play the DDJ-SX2 which will tick most if not all of your boxes. I am gonna be guessing that the Reloop Terminal Mix 8 does the same. Clearly there is the Numark NV as well. Not too sure where it sits, boxes ticked.
As for controllers and windows/mac. All DJ software that I know of works on both Mac and Windows. With the possible exeception of DJay Pro, which is Mac only. The hardware couldn’t care less what you hook it up to. And if you move to Mac, there isn’t that much of a learning curve to using a Mac and the DJ software will be identical to the windows version.
The DDJ-SX2 is a standalone mixer as well, so with the money left over from your budget, you could get one or two mediaplayers (regardless of which, I have two Numark NDX500s) that you use for CD/USB-stick backup in case of a windows crash.