I think the 固執, 好死板, 平時咁樣,
便咁樣 is only his personality. And the 如果做不到某時,他好發忟憎 is because children at this age , their brain development grows much faster than their physical development. They simply knows how to do things but they physically cannot do it that will make them very frustrated. That is normal. But if you are still worried, you can bring your child to the doctor and ask.