How to handle the supervisor that constantly worries I will subs

Sorry for not being able to type Chinese.

Don't know where his worries coming from. He's been working here for 5 years and I've been here for just a month. Everyday he worries about being fired. He worked about 100 hours a week. It seems the more he gets, the safer he felt. 

We are not in the same office and I can feel he wouldn't share his previou work. Sometime I thought if he's busy, he can just throw me what he did so I can figure it out myself instead of asking him. But he thought me being "needy".  

I never thought of taking his position. All I care about is to secure my job. But I worries his sensitivities could lead to some issues... Maybe I thought too much.