First, the job of the police is mostly to deal with crime. Landlord/tenant disputes are civil, not criminal. So no, the local police are not required to aid you in a civil dispute. That is a matter for the courts. I also would not trust them to know the law.
The law does not differentiate between landlord/tenant rights and responsibilities based on the relationship of the landlord to the tenants. If a police officer told you that he doesn't know the law.
However, the law is not very much on your side here. Since you do not have a lease, your tenancy can be terminated at any time with proper written notice. Proper notice for TX is one full calendar month if you pay monthly (Texas Property Code - Section 91.001. Notice For Terminating Certain Tenancies - Texas Attorney Resources - Texas Laws
The landlord cannot assault anyone. If there is proof of assault, that IS a criminal matter and should be prosecuted. On the other hand, with no lease, the landlord can have a say in who lives there. But, again, to remove anyone, prevailing law has to be followed. But, if the laws are followed, then they have to move.
Clearly the landlord is making things uncomfortable, so I would look for alternative lodgings.