At my job my manager has repeatedly what he has admitted are empty threats against my job for 9 months and has has also made demeaning comments towards me in front of other employees such as "did you eat lead paint chips as a kid?" I was wondering if this seems like it would qualify as harassment based on the fact that it creates a hostile and intimidating work environment or am I simply overreacting? I would like to hear some other opinions.

I don't think your over reacting. It sounds very demeaning and they are acting like a bully. Harassment yes, no professional person should be like that.
It almost sounds like they are trying to get a comical reaction from the rest of the employees.. i.e. 'watch me insult my employee' and expect a big laugh. High School all over again.:rolleyes:

But harassment is not actually illegal unless it is for specific reasons, race, religion and so on.

Next you are expected to have done something to make it stop,

Have you
1. told him that it is wrong and asked him to stop
2. reported it to the HR manager or his supervisor