Updates: He backed off.

Can be that the PM email worked - I told her that the problem is not something wrong with our process or programs, the problem is we are short of staff so a superhero comes to rescue and try to REBUILD/FIX a working ship will not help; or fianlly he knew what our top priorities are now, also, it can be that he couldn't figure out thousands of lines coding I had to handed to him multiples times (not sure why he kept asking for the same thing).

So far, I am happy that he can leave me alone so I can focus on deliverables. Wish me good luck and hope it stays this way.