Being an elite athlete (15-20 hours of practice a week) takes a huge toll on the body and you have to keep the prehab up to par with the shear and tear that accumulates over time as practice goes on.
Fish oil and Turmeric powder are good anti inflammatory agents as stated above and should be a part of any elite level athletes diet with or without inflammatory issues, as it will keep it at bay, for a time.
But supplementation alone won't get you very far and from your text above it is clear that the issues you are trying to combat cannot be fixed by any supp.
I'd recommend getting a foam roller and foaming the shit out of every inch of your body, before and after training, every single day.
I'd also recommend doing some heavy neck flexion with a harness, making sure to get your neck stretched every single rep before flexion. Getting your head snapped repeatedly fatigues the neck muscles, which is why they are an effective tool for wrestling. Getting some heavy flexion in there with the dynamic flexion caused by your opp's will help out a lot with both the range of motion and to resist being snapped as far as you would otherwise, leaving you less fatigued.
Lastly I'd recommend seeing someone who can help you out with your scar tissue, like ART.