Is a son obliged to obey his father's command to divorce his devout, committed Muslim wife, and can Ibn Umar's hadith be cited in such a case?

Obeying one's parents by divorcing one's wife is not obligatory. If a son does so and then regrets it, he may take her back if possible, especially if there is a benefit in doing so, such as safeguarding the children. Otherwise, there is no blame upon him.