To finish this off a have a little analogy for you.
If you have a room (10ftx10ft) with a tonne of teenage boys in it, and only open the window/door once a week, it's going to reek, even though you have fans running in the room.
This is the case with your planned tank. Small tank, Too many fish and one filter, sure its a good one, but still, that is a LOT of ammonia.
Continuing on with the analogy, what if most of the boys were crazy ADHD, one was a big bad bully who beat people up and then a couple innocent little kids for them to pick on.
That is your tank.
Finally, there will be literally no room for the fish to move in this tank without bashing into another fish.
As I stated at the start, it's okay to make mistakes. We all do. But please don't actually do this once you have been advised not to!