I'm not sure about the tang question, you have a big tank and they MIGHT get along but it's likely that they will not.
I have 30 Turbo snails in my 72gal tank and a few have died off, mostly from being attacked by some of my hermit crabs wanting a bigger shell. It's a little funny to see this little hermit crab trying to carry around this huge turbo snail shell, hoping to grow into it! I need to add some empty shells for the little guys.
Anyway, you might try to leave out the lettuce. I've never had a hipo tang but they probably would eat the algae if they had to. What happens is the tang eats the algae until it's just a little stump. Then it's short enough for the snails to finish off. Snails cannot eat the long "hair algae" until a tang or whatever shortens it for them.
Most of the time your lighting needs to be on for 12 hrs. I leave mine on for 15 and don't have any algae problems. If your bulbs are old (older than a year) then you may need to replace them or upgrade to MH or PC lights (or VHO). Algae likes to grow in dimly lit aquariums where the light is of the wrong spectrum. As lights age, the color shifts and includes wavelengths that encourage algae growth. New bulbs are bluer and have less of the red and green to cause algae to grow.
Once your coralline starts to grow, it will overtake the hair algae and eventually kill it all off. Once I got my snails it took about two weeks until all the hair algae was gone. It has never come back either and now I have cool looking coralline everywhere.
