You are going in the right direction. Try to toggle the melatonin to fit that niacin dose. Up the melatonin to 220mg and stay at 600mg niacin and see what happens.
It sure as heck can. Now you're getting the idea of how impossible it would be to make a product. In my eyes that makes it a good thing.
The ratio isn't exactly a linear curve when upping the dose. And for older folks with seriously depleted melatonin, it can take a while to replenish. The light flush means your pretty close to the sweet spot. Try 250 next time.