Al Qayyim is one of the names of Allah. How can the name of the scholar, Ibn ul Qayyim, be valid since it would mean the ‘son of Allah’?

The name of the scholar is not Ibn-ul-Qayyim. It is Ibn al-Qayyim al-Jawziyyah. Qayyim means superintendent or supervisor. His father was called Qayyim because he was the superintendent of al-Jawziyyah School, one of the famous schools of Damascus.