Hi again - yes, a pretty tank you have there!
I've taken no offence - my advice is offered purely for the sake of the wellbeing of the fish but you are the one who ultimately must make the decisions and choices and deal with problems if/when things go wrong. No one can force you to do anything you don't want to do. It's just advice. And you came on here asking for advice...
One thing I would like to point out, though, is that when we talk about a tank being "overstocked" it is not necessarily anything to do with how much room the fish have to swim about in. I mean, if that was the case you could probably shove another 50 shoaling fish in your tank and they'd still be able to swim around fine, albeit in a stressed state.
You have to take into consideration the size and output of your filter. If the tank holds too many fish for that volume of water and filter, the filter bacteria can struggle to keep up with converting the amount of ammonia that will be present throughout the day. If your filter media can't keep up with it all, this is when you end up with an ammonia spike in your tank, which you already have.
Running two filters (or an extra powerful one) is definitely a good idea on an overstocked tank but you still need to do very regular water changes to keep the nitrates down.
It can all become very stressful and tiring soon enough - and when you want to take a short holiday somewhere you then have the bother and worry about who will do these water changes throughout the week... it can, in time, take the pleasure out of fishkeeping. On a tank that is not overstocked and well-maintained, water changes can easily be left for a couple of weeks or more (e.g. while you are holidaying or maybe sick in bed...) with no ill-effects to the fish. But leave a heavily overstocked tank for 2 - 3 weeks without a water change and chances are you'll lose some fish or find disease has crept in...
Another thing to bear in mind - fish grow fairly quickly. Those sizes you quoted are the current fish sizes - you can double or treble some of those - and it is the adult sizes you should use when working out a stocking level.
Anyway, that's enough from me. All the best - Athena