The way I got my tangs to eat nori was by folding it (so it looked kind of like a greeting card or whatever), then cutting almost all the way to the fold to create thin strands of nori, so that it ended up looking like a comb. I don't know how to describe it. Basically you want to present the nori as a bunch of thin strands. I find that having just a flat piece of nori, even if it's only an inch in size, is intimidating for fish who don't know about nori. If it's in thin little strands that can easily be singled out by the fish and easy pulled off without much effort, the fish is far more likely to eat it.
Also, see if you can buy some live sea lettuce (Ulva). You can get it at Algae Barn (USA) or at Gulf Specimen Marine Lab (international). You can also buy live red nori from them as well. Buying live copepods wouldn't hurt either.
Have you specifically tried the Hikari Omega Enriched Brine Shrimp yet? It's the only thing I can get my carnivorous nano-fish to eat (Dario dario, bumblebee gobies), and it's one of the few things my wild-caught (thought I was getting captive-bred) pyjama cardinalfish will eat. Even fish who refuse to eat get extremely excited at the smell of the Hikari Omega Enriched Brine Shrimp. They must use some sort of proprietary blend of omega acids. Oh, you can also try culturing some live baby brine shrimp to see if it triggers a feeding response.
You should also try buying LRS Fish Frenzy, and if you can find it, LRS Fish Eggs. Heck, try to find some PE Mysis Shrimp. I can tell you my tangs were total carnivores when we brought them home (they aren't fully grown yet, but they're nowhere near as small as tangs you see for sale at stores). I don't think they'd touched a single piece of nori or algae in their entire life.
Also, I'd recommend covering the other three sides of the tank with paper (preferably black), leaving only the front part uncovered. This should make him feel more secure (it works with birds at least), and prevent him from getting distracted by reflections. I know this isn't common practice, but you could also maybe try put substrate on the bottom for him (don't use live sand since it'll probably just cause an ammonia spike).
I'm on the fence about removing the wrasse, since the wrasse might end up teaching him to eat the nori, since most animals can learn by watching others.
The only other thing I can think of is playing classical music for him. It sounds stupid, but playing classical music has been shown to have a positive effect in terms of reduced stress in dogs, cats, birds, multiple fish species, etc. The reef's a noisy place, and the only time the ocean's relatively quiet is when there's predators nearby or in open ocean.