I don't think you necessarily have to assume your boss is trying to fire you. It's good to take precautions in case, as others have suggested. However, he may just be trying to get you to work harder, or trying to prove you're not better than him or something.
When he looks over your shoulder when you're typing, you might try stopping (maybe closing the document) turning to him and saying "Did you want to talk to me about something?" or if he asks you to type so he can watch, you might keep saying "I'll email it to you in half an hour." or maybe even "Actually, it makes me nervous when someone watches while I type. I'll email it to you in half an hour."
I wanted to pull this out. You started to work at this job at the very beginning of the horrible period of the 2008 economic mess. You started to look for another job, also still in that period. I don't know what came before this job on your resume, but whatever it was, it was probably offset by the relatively short amount of time you had been at your job.
Originally Posted by Suelin23
The economy is still tight, but not as bad as it was then. You may want to retool your resume with your four years at this job. You also, now, should have more contacts from this very job (remember the private contractors? you could go to work for them).