"Non Dutch native working in childcare centres would mean their kids didn't learn Dutch properly". If those non-natives don't speak proper Dutch or with a heavy accent I could understand these parents, kids pick this up and it will influence their learning and future prospects negatively.
I am sorry you felt treated badly but that is not racist, a Dutch person would also get "fuck you" (rot op) if you ordered just for closing, especially because cafes close at 2am in Amsterdam.
You have to adapt to local culture, most people use debit cards and don't pay cash, especially not small items with large bills, if someone tries that, the bill is most likely a fake.
Calling to try to change resident registration?? If you could do that, anyone could easily commit fraud.
Some ghettoisation??? Yes, there are no-go areas, I lived there, try to get a taxi or uber at night going to the K buurt.
An enormous amount (like the average number of people living in a Dutch city) of non-western, low educated immigrants (>80% young men) are coming to Netherlands each year, there is no housing so the government is putting them into camps. This causes a lot of stress and criminality on the surrounding villages. Busses need to drive with police protection.