The pimples on a newborn are usually normal and a reaction to the difference in climate. Sometimes he could be reacting to something he eats.
Yellow stool on a baby that is seedy and mustard-like is normal for a breastfed child. If you are formula feeding, it can vary.
If the baby has very explosive BMs and seems to have a lot of gas, consider removing dairy from your own diet if you are breastfeeding. He should feel better within 2 weeks.
If you are formula feeding, then switch to a lactose-free formula or another kind that is more gentle on his stomach.