Some of your questions depend on the year model of the car, as the factory changed specs year to year. And secondly, which state are you going to register it in as smog controls could be a concern, especially here in California.
I do not see any problem with the first three questions. Yes we do have seat belt and key buzzers, but I don't know if they would be required. The bumpers and doors I don't know, but your year model could be standard to US specs.
You will probably get a lot of good answers in the next day or two from this group. good luck. Ed
By the way, where in the Netherlands do you live?