Honestly we can't answer that.
Have you looked at the California statutes about landlord tenants?
I would first of all talk to the actual owner of the property and see what they say. I don't think they will change locks, though. They may start evictions on you if he causes an issue - so it's best to get them on your side early on.
You know him best. If you think you can get away with just moving his stuff out, try that. Who is going to pay for the storage? He could drag that out for years, too. You can't rent storage in his name, you'll be responsible for payments and any damage he might do to the storage facility. I mean, you'll run into the same problem with his stuff in some storage unit as you are running into now. I wouldn't go that route.
Seems like he wouldn't try to get back in if all his stuff is out - but the police might tell you differently. Have you called the police for info? How do you know he'll just hand over the key to your place?
You can always break your lease and move out yourself. Might be cheaper than trying to hire an attorney and evict.