There hundreds if not thousands of videos of people keeping fish in tanks that are to small does that make it right? No. Also do ever see a 1 year or 2 year update on these videos? Most likely no because the fish either died and they sold the tank or the fish got to big and they sold their tank...
I think gallon size it's self is irrelevant it's the foot print of the tank that matters and a 55 doesn't have the foot print for tangs.
The 1" per 2 gallon rule is flawed if you have a 3" clownfish and 3" tang the bio load is not equal the tang eats more and poops more than clown. By that rule...
If two-three weeks is your idea of long term success then you are sadly mistaken. The fact that they aren't fighting with each other because they are in such small over stocked tanks with fish constantly coming and going and they can't "claim" a spot in it basically there is no pecking order...
What about in 6 months when those fish are bigger? a small fish may be happy in small tank but only for a short time you have to think about keeping them happy for life not till you get bored of them.
Also I'm not seeing a list.
Part 1 isn't horrible but the yellow tang and niger trigger will need a bigger tank. Part 2 is way over stocked those tangs should not be in that tank.
A hippo tang would have a horrible life in a 55 gallon tank I had one in my 135 and it used every inch of my tank. No tang belongs in a 55. Plus it's a column tank.
As far as ***** goes what they do is fish is just wrong. Just because you've seen one place do it doesn't make it right those small...
I would look at other small fish damsels are pretty aggressive and would probably kill the clownfish and or each other. Some good more peaceful substitutes would be fire fish, cardinal fish, chromis, gobies, wrasses and blennies.