I just got it all set up and sad to say, this isn't going to work the way you want it to with the mixer you have.
Here's the problem... rekordbox is designed for one audio interface. If you use the IF2, that is the device it will use for input of the timecode and output of the audio from rekordbox. That means even though you could control rekordbox with a CDJ, it can't be used as an output device.
ASIO4ALL can aggregate multiple devices together, however there's a catch in that it doesn't recognize the IF2 as a 4x4 device, it shows up as a 2x2, which means you could use it for timecode I/O, but only on one turntable... effectively making it an IF1.
I even tried using some other software to try and make it work, but it's quite complex when trying to get signal in from one piece of hardware, then send it to software, then send the output back out to that hardware as well as two other pieces of hardware.
Sorry, but I'm afraid the answer is either you need to choose either HID or DVS, or get a DJM capable of DVS support... or use a Mac, which I haven't tested, but have a theory on how it would work.