Not sure how CA is, but generally, if you want the benefit of separate entities for liability purposes, they need to actually be separate entities. You can have a holding company that owns each of the three businesses, but one EIN per entity and one DBA per entity. So you’d be looking at four companies. Typically you wouldn’t go by two names either, such as CompanyA LLC d/b/a CompanyB because legally, if DBA, then the DBA name should be used.
Also consider that a sole proprietorship does not limit your liability in the way a corporation would, anyway.
Grain of salt, and all that.