Hi Louise,
Those summaries primarily examine NAC and hearing loss. I've never read NAC helps with tinnitus, but it might prevent it from getting worse. Melatonin, however, does reduce tinnitus distress and volume, according to several studies listed on pubmed. Here's a link to a recent study:
http://www.ncbi.nlm.nih.gov/pubmed/21859051
I take 3 mg a night, but I still have difficulty sleeping as melatonin is short acting. I'm thinking of switching over to a time-release melatonin. I'm not sure on the dosage, but 3 mg is the amount you always see in the clinical studies. BTW, I don't believe you should take melatonin with antidepressants and other drugs, like Klonapin.
The one summary from your reference with melatonin and sulpiride appears frequently in tinnitus literature. Sulpiride is an antipsychotic. I'm not sure why anyone would want to take something like this. But since melatonin and sulpiride work on dopamine, it's possible melatonin might be combined with something like l-tyrosine, an amino acid and precursor to dopamine. At least, I'm thinking about combing the two if my current supplements lose their efficacy.
I also take magnesium (200 mg 2x daily); zinc (15 mg 2x); alpha lipoic acid (200 mg; 2x daily); GABBA (100 mg, 3x daily). I used to take l-theanine (a GABBA precursor) (3x a day) and it helped for a while, then it made my head buzz. I guess from too much GABBA. Finally, for ear health I take vitamins A,C,E.
Things that did not work for me include Vitamin B-12; coQ 10; and Gingko. All made my ears buzz. But these might work for you.
All the above mentioned supplements appear in the medical literature. While I believe these supplements have helped, I can't prove it. My improvement might be from the placebo effect. Or it could be the passage of time. I do know that diet will make me spike. As will many noises. So for now, I'm keeping to my diary and my current supplements and hoping for continued improvement.
I hope you find something that helps.