How long would you reckon?
(I’ve got sbb corals I’ve needed to pickup for the last month and I keep holding it off

)
How long depends how much effort you put in. Small tank has advantage to be cleaned very quickly and easily (just like on the flipside it has disadvantage to become polluted very quickly and easily). If you follow my suggestion, you should see improvement in days, mostly clear tank within weeks.
Syphon your sand, all that uneaten food is now stored in the sand. Syphon and then pinch the hose to make the sand go back down, but all the silt will be sucked out. The change out water will be black, so keep changing water by syphoning the sand until the water becomes clear. The sandbed is feeding the algae so clean the sandbed out.
Feed only 5-6 pieces of food to your fish, do it 2-3 times a day.
Understand this - poop is not 100% poop, poop includes about 20%-40% uneaten food, this is what the cuc will eat, you don't need to feed the cuc.
Get the smallest cheapest powerhead from
amazon (about $12-$15) for your tank, you must have flow, more than hob filter can provide.
Put some activated carbon in your hob, this will help absorb more dissolved organics.
Scrub the hairiest parts of your rock with a toothbrush daily. Syphon out the algae that releases from the rock.
If you do this, the bright green will start to disappear in days. Get rid of some snails, you will control the nutrients so they should not have enough to eat and will die. That many snails might create an ammonia problem if too many die at once. Just keep 2 or 3 of each. Good luck