Ok SO, this is not good. Always pay attention to the feeling in your stomach. I think you might want to go down to the police station and just talk to them. You dont have to file for a restraining order, but you might want to start to get some of this on record. If you feel in danger or threatened, then a restraining order might be necessary.
There are certain criteria that have to be met in order to obtain a restraining order (I unfortunately had to go with a friend who needed one).
Knowledge is power. Go talk to someone. And please do not answer his texts particularly with a threat.
Now I am really concerned. Please let me know what happens.