2. Talking to managers and tell them I would leave.
3. Giving him the attention and greet him when he wanted to do something good.
4. Hear his opinion.
5. Remind him my role when power argument arise.
6. Indifference and segregation also worked well. The company started to avoid him.
If none of these calm him, then I would simply leave. There´s no need to gift life and sanity for a jerk.
It shouldn't be a problem. In science, everything must be tested and proved if you want to know the truth or the effectiveness of an theory. Design is a science, so it can be measured and developed by tests of all kinds, even emotionals.
Whereas a design studio with sufficient resources should fare better with a data-driven approach, a sole designer or small team with time and feedback constraints will probably do better with traditional methodology. Traditional methodologies might have certain quack dogmatic rules and processes, but it offers a battle-tested baseline.
I have never installed Snapchat. I don't know if it is good or bad. All my friends doesn't have Snapchat, but everyone has Twitter. I found Twitter a better place, and it's ageless to me compared to all those new-UI paradigms that come each year. The problem of Twitter is they cut off all the innovation of 3rd party software developers to keep their shitty in house software.