It seems to be impossible for a single person to match all the descriptions defined in that link but I met some people in my life that have matched to some of them and my advice is "avoid them at all cost". Please note the above statement is just for as far as the link concern I believe Alex is not in that description, I don't even know him.
Well, if he has your real name and is making threats against you you should call the police and file some sort of report against him. I mean, if this is as serious as you are making it out, you need to take real action.
I don't know if he really knows me because he didn't say so in the emal. At any rate, I am taking appropriate action just in case. Better to be safe than sorry in matters like this.
Threats again your alias on ET are hardly worth going nuts about. If he knows who you are, then thats an entirely different story. What would give you the idea that he would even know your real identity?