How can one reconcile God alone giving life and death and blowing the spirit into the dead and the fetus, with the angel blowing the spirit into the fetus?

Allah alone is the Creator of causes and their effects. The occurrence of what is decreed through a cause does not contradict His sole creation and decree. Everything in this world and the Hereafter only comes into being through a cause. Allah is the Creator of causes and their effects, and these are not independent in their effects; rather, they require other causes and may encounter obstacles. The angel's blowing of the soul into the fetus is by Allah's command, will, and power, and it does not contradict His exclusivity in giving life.