1. Try Blackhole software https://github.com/ExistentialAudio/BlackHole/releases
(replace soundflower)
2. Use Blackhole as a default sound output
3. With your DDJ connected and powered-on, open rekordbox, and click the PC Master Output to enable the dual-output mode. This will send the master output both through your DDJ's master out as well as to a secondary output within Blackhole (Like in step 2 https://forums.pioneerdj.com/hc/en-us/articles/115004807346-Streaming-with-OBS-a-DDJ-Windows-)
You will have DDJ-1000 MASTER + Blackhole 16ch (in Preferences/Output Channels)
4. In OBS you have to set Blackhole 16ch as Audio Input Capture
Working like a charm ;)
Best !