You should be able to bring that to a stop fairly quickly.

Are you sure you have disabled DC braking and instead enabled the braking resistor? I wouldn't expect the braking resistor to hold off until you get down to 3000rpm. It doesn't care what the speed is, only that the internal DC voltage is trying to exceed that threshold value and needs to be kept in check. That voltage surge is due to trying to decelerate the spindle rapidly and regenerating the energy back into the inverter. Which is why the decel time and threshold voltage are the only parameters that really matter here. If the braking resistor mode isn't enabled, the only thing limiting the voltage is the losses in the drive. On the other hand, 5kW should fairly rapidly burn off the RPMs.

If it's a proper braking resistor, the 5X factor should be fine as long as the "1kW" figure is a continuous rating. Ultimately the limit is the melting point of the resistance element inside the resistor. They are made of wire or foil so they have a decent thermal mass. Other, more common resistors use carbon film which can't withstand much energy before burning out.