I doubt this will constitute "stalking" under CA law. Not only must the actions of the person be willful and malicious, they must be accompanied by some manner of threat or behavior that gives you good cause to fear for your safety or the safety of your family. And that cause must be something more than your "thinking" he might be dangerous.
A restraining order is possible, though it might cost you upwards of $250 for a civil restraining order (maybe less ... it depends on your county). However, since it seems there is some sort of business arrangement between the two of you (for the furniture, etc.), a judge is likely going to balk at issuing a R/O unless the contacts are something more than attempts to get you to pay what he thinks you owe him or to re-think the deal.
Much will depend on what actions he has taken and what he has said. Simply being a pain in the tail end is not enough for a R/O.
If you think you have a case, go to the county court house and ask how you can file to obtain a restraining order. The process is relatively easy, and depending on the county you live in, you may even get before a judge the same day ... but don't count on it.
If he makes threats or refuses to leave when you tell him to leave, call the police and report him for the threats or for trespassing. If he makes similarly annoying and threatening phone calls, notify the police and file a report for annoying and harassing phone calls. None of these will likely result in his immediate arrest, but they might serve to start a paper trail on the problem ... IF what he is doing actually rises to criminal acts.
- Carl