The door seal problem is common, it's the way they are designed and there's nothing you can do. Some are better/worse than others but there has to be a surplus of door gasket which lets water accumulate so that when on spin it doesn't tear or get pulled off. Basically the door seals are oversized in that area to allow movement on spin.
The small plastic ball in the sump hose is there to seal off the sump hose and prevent detergent getting into the sump and being wasted. They definitely aren't essential and were only invented about 15 years ago. I wouldn't think it necessary to remove it as it may well never cause a problem. It will only cause a problem if the washer gets gunged up because you only use liquid detergent and low temperature washes and never do a monthly maintenance hot wash.