I've always used the rule of thumb that a tank should be 6-8 times longer than the fish. This 'rule of thumb' assumes that the tanks proportions are roughly in the ratio of 4:1.
Obviously, that needs to be applied with a degree of sense and sensibility.........
Generally, for very active / cruiser fish ..... the type that never keep still (like your pink tail or niger), then apply x8 times. For slower but nonetheless active fish such as butterflies or your picasso, you can apply the x6 times.
So, correctly aquascaped and notwithstanding inter-species aggression / territorial concerns / biological capacity of the tank, then your tank is good for the pink tail and niger until its about 7-8" long..... maximum...... but the niger will keep growing well past this..... the pinktail too, but no nearly so quickly.
My opinion is that what you will find over the next 12-24 months is that the bioload limits of your tank will peak meaning you'll need to do more and more maintenance. You will begine to see a decline in the colour and health in the percs, filefish, and butterfly. You will then see a decline in colour and slowing growth rates of the other fish, as well as increasing algae problems etc. This will be attributed to (a) water quality and (b) stress induced by territorial matters. They may not "fight", but the stress will be there.
In conclusion, I would say you are ok for now, but monitor things closely and if you find the fish are looking as good as they once did, its time to take corrective action. But this comes with a caveat - if you wait until the triggers begne to exercise the agressive tendancies, then a strict pecking order will have established itself - removing fish from that pecking order will upset everything no matter whether you remove the alpha or someone in the middle...... relationships are dynamic and change according to environment. To that end, I would advise that you should now start picking favourites and thin your stock out now - perhaps replacing some potentially bigger fish with potentially smaller ones - i.e. maybe swap the niger for a yellow tang (just an example).
Hope this all helps.